|For an essay on developments in psychology from 1967 (when I took introductory psychology as a college sophomore) to 2017 (when I taught my last intro class and retired from the University), see "50 Years of Psychology: A Personal Look Back a "Intro".|
William James (1842-1910), the great Harvard philosopher and leader of early American psychology, famously defined psychology as "the science of mental life" (in his Principles of Psychology, 1890). The goal of psychology as a science is to describe and explain states of mind -- or, as we would now put it, the mental structures and processes that underlie human experience, thought, and action. Quite simply, the task of psychology is to understand how our minds work, just as the job of physics is to explain how the physical world works, and the job of biology is to explain how living things work, the job of sociology is to explain how societies work, and the job of political science is to explain how political institutions work.
But what exactly does the mind do?
In the 19th century, a group of
theorists known as the phrenologists, led by Franz
Joseph Gall (1758-1828) and Johann Gaspar Spurzheim (1776-1832)
attempted to classify all the things the mind did, and relate
each activity to a particular part of the brain. Gall came up
with a list of 27 "mental and moral faculties", and Spurzheim
added 10 more. The phrenologists distinguished between various
kinds of love (physical love, parental love, friendliness),
different aspects of perception (form, location, color, tune,
and time), different kinds of thinking (comparing and causal
reasoning), and various traits and attitudes (wit,
secretiveness, benevolence, and conscientiousness). That's a lot
of mental functions, and even so the phrenologists got into
debates over precisely how many there were. (We'll talk more
about the phrenologists in the lectures on the Biological Bases of Mind and
But even before the phrenologists arrived on the scene, a succinct answer was provided by the German philosopher Immanuel Kant (1724-1804), in his famous (and pretty much unreadable) Critique of Judgment (1790):
"There are three absolutely irreducible faculties of mind: knowledge, feeling, and desire".
In other words, mental states consist of the thoughts, feelings, and desires that pass through our minds when we're conscious. It is my virtue of our minds that we acquire and use knowledge, and experience emotions, moods, needs, and wants -- how we know things, feel what we feel, and desire what we desire. By saying that these states were "irreducible", Kant meant simply that thoughts, feelings, and desires were in some sense independent of each other, and one was not derivative of one or more of the others (this is a controversial point, and not all psychologists accept it, as we'll see in our discussions of emotion and motivation).
- cognition, having to do with knowledge and beliefs (perceiving, remembering, thinking, learning, problem-solving, communicating, and the like);
- emotion, having to do with affect, moods, and feelings (of pleasure, pain, and the like); and
- motivation, having to do with drives, needs, desires, purposes, and goals (tendencies to approach and avoid, and the like).
So, the scope of psychology is very broad, including:
- questions about basic processes, or how the mind works;
- the origins of mind, in terms of the evolution of the species and the development of the individual;
- individual differences in the organization of mental life;
- pathology, the disorders of mind that characterize various mental illnesses;
- applications of psychological knowledge in education (enhancing teaching and learning), psychotherapy (prevention and treatment of mental illness), the workplace (enhancing worker productivity and managerial effectiveness), and the like.
Why do we care about these mental states? At the very least, we care about them because thoughts, feelings, and desires are things we experience, and we want to know more about them -- just as we want to more about the stars in the skies, the earth beneath our feet, and the other creatures that live here with us.
But more than idle curiosity is at stake here. We want to understand how our minds work because we believe that mental states play a causal role in our behavior. The underlying philosophical rationale for scientific psychology is the doctrine of mentalism, which states in formal terms, that
Mental states are to action as cause to effect.
In other words, that what we do depends
on what we think and feel and want. Understanding how our
minds work, why we think and feel and want as we do, then, is
essential to understanding why we do what we do.
Psychology is the science of mental life, but it's also one of a
number of behavioral sciences like anthropology or economics,
political science or sociology. All the behavioral
sciences are concerned with understanding the behavior of human
beings and other animals -- how individuals interact with the
physical world and with each other. But each of these
behavioral sciences has its own preferred way to explain why we
behave the way we do.
For example, consider a rather dramatic behavioral observation: that some person, X, has committed suicide. The question naturally arises: "Why did he kill himself?". Psychology offers three general types of answers for consideration:
- a cognitive explanation,e.g., " X killed himself because he believed he was worthless";
- an emotional explanation, e.g., " X killed himself because he felt worthless"; or
- a motivational explanation, e.g., " X killed himself because he no longer wanted to live".
A psychological explanation of behavior explains an individual's action by invoking his or her mental states. And psychology, as a science, seeks to understand the nature of these cognitive, emotional, and motivational states: how they relate to each other, how they relate to what is going on in the brain and the rest of the body, and how they relate to the individual's behavior.
Not everyone agrees with this idea, by the way. Some philosophers (and some psychologists, too) dismiss mentalism as mere folk psychology -- a set of naive, traditional ideas about the mind and behavior, unsupported by scientific evidence, that are doomed to be replaced by a more sophisticated, truly scientific view.
- According to the most radical of these views, our mental states are epiphenomenal, and play no causal role in behavior. From this point of view, folk psychology is something to be abandoned as science progresses, just as we have abandoned concepts like phlogiston and ether.
- According to another view, known as reductionism (see below), psychological theories are only halfway points in the explanation of behavior, and that truly scientific explanations are found at the biological level of neural interactions, or even at the level of physics and chemistry.
The Domain of Psychology
Psychology is a behavioral science, one of a number of disciplines (including anthropology, biology, economics, history, political science, and sociology) that seek to understand how individuals (whether humans or nonhuman animals) interact with each other and the world in which they live. Each of these sciences has a particular scope, and a particular set of concepts by which it seeks to explain behavior. As described above, psychology explains behavior in terms of the individual's mental state -- the organism's thoughts, feelings, and desires.
Herbert Gintis, an economist, has suggested that all the behavioral sciences are united around the following principles:
- As a species, humans have certain universal characteristics which are the product of their evolutionary history.
- Genetic changes form the basis for cultural evolution.
- Cultural transmission is generally conformist.
- Human preferences are socially programmable, by which individuals internalize norms.
- Human interactions are strategic in nature.
- The brain is a decision-making organ.
- Individuals generally act rationally.
This is a good start, though
we can quibble about some of the points. Three things,
however, are for sure:
- The mind is a decision-making organ.
- The mind is what the brain does.
- Human action, including social interaction, is determined by these decisions.
Psychology as a Social Science
Psychology is also a social
science, because humans are social beings as well as
intelligent beings. We live in groups, rather than in isolation,
and we cooperate and compete and make exchanges with each other
on a daily basis. Our individual mental lives take place in this
social context, and so we have to understand it in order to
understand what we think, and what we do. Accordingly,
psychology must be concerned with a number of problems:
- Social Interaction: how individuals relate to each other in the ordinary course of everyday living.
- Social Influence: how other people, as individuals and in groups, influence the individual person's experience, thought, and action; and, reciprocally, how individuals influence the groups of which they are part.
- Social Cognition: in general, social psychologists take the position that important social interactions are cognitively mediated: that the way we behave with each other is determined by our knowledge and beliefs about ourselves, others, and the situations in which we encounter them. Accordingly, psychology is interested in how we form impressions and make judgments concerning ourselves, others, and social situations, and how we encode and retain social knowledge in memory. The repertoire of knowledge and skills that we use to navigate the social world is sometimes called social intelligence.
- Cultural Psychology: psychologists are also interested in the impact of sociocultural factors on individual cognitive processes -- e.g., do people in different cultures think differently?
- Emotion and Motivation: for largely historical reasons, the study of emotion and motivation has largely been the province of social psychologists (although this situation is changing, and emotion and motivation are emerging as independent sub-disciplines within psychology, much as cognition is now).
- Personality: psychologists are also interested in
individual differences in mental functioning, the origins of
these differences, and their expression in social behavior.
"No man is an island", as the English poet John Donne put
it. These individual differences are usually manifested in
social situations, or at least become apparent in social
In general, while cognitive
psychology studies mind in the abstract, social psychology
studies mind in action, or mind in social
relations -- how beliefs, attitudes, and other mental
states translate into interpersonal and inter-group behavior.
Psychology as a Biological Science
The brain is the physical basis of the mind, and so psychology must also be a biological science. The attempt to understand how the mind works naturally leads to questions concerning the biological basis of mental life --the anatomical structures and physiological processes involved in cognition, emotion, and motivation. Accordingly, psychologists are interested in a number of biological topics, including:
- Neuroanatomy: the structure and organization of the nervous system.
- Neurophysiology: the neural processes involved when we perceive an object, shift our attention, remember something, speak, listen, write, or read to another, feel sad or happy, hungry or thirsty, dream, and hallucinate.
- Molecular and Cellular Biology: how neurons work, and how they communicate with each other. In particular, because memory is recorded in connections among neurons, psychologists are interested in the molecular and cellular changes that accompany learning, remembering, and forgetting.
- Endocrinology: the nervous system is one way that
various parts of the body communicate with each other; the
endocrine system is another. In particular, psychologists
are interested in how hormonal changes affect mental
functioning, and how mental processes, operating through the
nervous system, might affect the body's hormonal environment
-- a topic known as psychoneuroendocrinology.
- Immunology: It is also widely held that stress and other emotional states, again operating through the nervous system, can affect the body's vulnerability and response to disease -- a topic known as psychoneuroimmunology.
- Genetics and Evolutionary Biology: the field of behavior genetics is concerned with hereditary influences on mental and behavioral processes, while the field known as evolutionary psychology, a successor to sociobiology, is concerned with the evolutionary origins of human experience, thought, and action.
Interestingly, modern biology
has an expressly social aspect, ecology, which
is concerned with the study of interacting how groups of
organisms, such as species, each of which occupies its own
environmental niche. Ecology is concerned with the organism's
adaptation to its environment, and its relations with other
organisms. For humans, mental processes play a crucial role in
adaptation and interaction. For this reason, psychology may be
viewed as part of an interdisciplinary field known as human
Psychology as a Physical Science
- In fact, some of the earliest scientific psychologists
were interested in psychophysics, which
traces the relations between the physical properties of
stimuli and the psychological properties of the
sensory-perceptual experiences to which they give rise.
- More generally, knowing how the nervous system works as a
physical system can help us to understand how the mind
works. Consider, for example, the importance of optics, a
branch of physics, for understanding our sense of vision.
- More recently, advances in biophysics have led to the development of brain-imaging technologies, such as PET (positron-emission tomography), MRI (magnetic resonance imaging), and MEG (magnetoencephalography), which allow us to see the brain at work while subjects perform various mental tasks.
Levels of Explanation
The idea of psychology as a physical science, at least in part, raises the question of reductionism -- the idea that the principles of psychology can be reduced to principles of physical science. Such a reduction would allow us to eliminate reference to such "folk-psychological" terms as belief, attitude, and the like, and explain behavior solely in terms of neural functions. The question is whether knowing the physical state of a person's brain will allow us to predict his or her thoughts, feelings, desires, and actions.
The doctrine of reductionism was succinctly stated in a quotation attributed to Ernest Rutherford (1871-1937), a British physicist who won the 1908 Nobel Prize (ironically, in chemistry!) for his work on radiation:
There is only one science, and it is physics; all the rest is stamp collecting.
Reductionism is particularly
favored among physicists and psychologists and philosophers who
might be diagnosed as suffering from "physics envy", and it
remains at topic of considerable debate among psychologists and
Here's a nice example of biological reductionism. Zietsch et al. (2-15) reported a genetic study of marital infidelity -- what the biologists euphemistically call "extra-pair mating". In a group of more than 7,000 twins and siblings, they calculated that about 53% of the variability in infidelity was due to genetic factors (62% for men, 40% for women), and the rest due to environmental factors. Moreover, by genetic typing of a subsample of the subjects indicated that infidelity was associated with the presence of any of five variants (technically, single nucleotide polymorphisms) of a particular gene, known as AVPR1A. Now, Zietsch et al. were very careful not to be reductionistic. They pointed out that genetic and environmental variance were split about 50-50 (when the two sexes are combined). And they also pointed out that, while genes might contribute to the motive to be unfaithful, the environment provides the opportunity to do so. Nevertheless, some commentators immediately jumped to the conclusion that, when it comes to marital infidelity, "our genes make us do it". For example, writing in the New York Times, Richard Friedman, a prominent psychiatrist, wrote the following ("Infidelity Lurks in Your Genes", New York Times, 05/24/2015):
We are accustomed to thinking of sexual infidelity as a symptom of an unhappy relationship, a moral flaw or a sign of deteriorating social values.... But... it turns out that genes, gene expression and hormones matter a lot.... We have long known that men have a genetic, evolutionary impulse to cheat, because that increases the odds of having more of their offspring in the world. But now there is intriguing new research showing that some women, too, are biologically inclined to wander, although not for clear evolutionary benefits. Women who carry certain variants of the vasopressin receptor gene are much more likely to engage in "extra pair bonding," the scientific euphemism for sexual infidelity.... For some, there is little innate temptation to cheat; for others, sexual monogamy is an uphill battle against their own biology.
In the final analysis, however, psychology links three different levels of the explanation of behavior: the psychological level, emphasizing the individual's mental states; the sociocultural level, emphasizing social structures and processes external to the individual; and the biophysical level, emphasizing physicochemical structures and processes. The psychological level of explanation has links "up" to the sociocultural level as well as links "down" to the biophysical level, but psychologists must favor explanations of behavior that refer to the individual's mental states.
- At the psychological level of analysis, psychologists explain behavior in terms of beliefs, feelings, and desires, as described earlier:
- At the sociocultural level of analysis, however, it may be that suicidal behavior can be influenced by social and cultural forces.
- For example, in World War II, Japanese kamikaze pilots obeyed the orders of their superior officers.
- And the members of the People's Temple in Jonestown, Guyana (originally based in Oakland) obeyed the orders of Jim Jones, their cult leader to "drink the Kool-Aid", leading to the mass suicide known as the "Jonestown massacre".
- Or, for that matter, the perpetrators of the terror attacks of September 11, 2001, ostensibly done in the name of Islam.
- At the biophysical
level of analysis, suicidal behavior may be
influenced by genetic predispositions (if, for example,
suicide ran in families), or by certain neurotransmitters or
- For example, identical twins are more alike in their
suicidal tendencies than are fraternal twins, suggesting
that there is a genetic (as well as an environmental)
predisposition to suicide (there is also an environmental
component to suicide, as we'll discuss later in the
lectures on Psychological
- Suicide also seems to be related to a disorder in the serotonin system in the prefrontal cortex of the brain (see "Why? The Neuroscience of Suicide" by Carol Ezzell, Scientific American, 02/03).
Suicide is very complex. For an up-to-date overview of the literature, see Suicidal: Why We Kill Ourselves (2018) by Jesse Bering. And if you're having suicidal thoughts, call the National Suicide Prevention Lifeline at 1-800-273-8255.
Each of these levels of analysis is appropriate, and is favored by particular disciplines (sociologists and anthropologists prefer the sociocultural level of analysis, while geneticists and neuroscientists prefer the biophysical level). A biophysical analysis is not superior to a psychological or a sociocultural analysis; the levels are just different. No level is more legitimate than any other, and none carries any special privilege.
However, the three levels of analysis are almost certainly interrelated. For example, a discipline known as sociobiology (a term coined by the evolutionary biologist E.O. Wilson) attempts to account for various sociocultural phenomena directly in terms of biological processes such as evolution by natural selection.
From a psychological point
of view, however, the processes studied at the sociocultural and
biophysical levels of analysis generally find their pathways to
the individual person's behavior through the psychological
level. For example, a person's suicidal behavior may reflect his
belief in the authority of a charismatic leader or the
righteousness of a cause (Japanese kamikaze pilots
during World War II, the residents of Jonestown, Guyana, the
suicide bombers of the Middle East, or the terrorists of
September 11, 2001 come to mind). Alternatively, his feelings
of depression may be the product of genetic predisposition, or
engendered by certain hormonal changes.
When all is said and done,
however, psychology, as the science of mental life, includes all
three levels of analysis, and tries to link them together by
asking the following sorts of questions:
- How does the mind work?
- What is the relationship between mind and body?
- What is the relationship between the individual and society?
Psychological explanations of
behavior are always at the level of the individual's mental
state, but other levels can also be of interest for what they
tell us about the mind -- the sociocultural matrix in which the
individual resides, and the biological bases of mental life.
The Philosophical Backdrop for Modern Psychology
The questions about mind addressed by scientific psychology have their origins in age-old philosophical questions. These have been summarized as follows by the philosopher Thomas Nagel:
- How do we know the world?
- How do we know the contents of another person's mind?
- What is the relation between mind and body?
- How do words acquire meaning?
- Do we have free will?
- What is good?
- What is just?
- What happens when we die?
- What is the meaning of life?
The same sorts of questions were posed in another way by the artist Paul Gaugin (1848-1903), in the title of one of his famous "Tahitian" paintings: Where do we come from? What are we? Where are we going? (1897) Note the baby on the right-hand side of the painting, with the elderly woman on the left.
Historically, psychology is an offshoot
of philosophy, addressing these philosophical questions about
the mind with the tools of empirical science. (Psychology is an
offshoot of physiology as well, as some of the earliest
scientific psychologists worked on problems of sensation; but
that is another story.)
A Comic-Book History of the Philosophy of Mind
It should be understood that there was a time when nobody, not even philosophers, were asking questions about the nature of the mind. Before the 9th century BCE, questions about mental life weren't discussed by philosophers, at least in the West. Julian Jaynes, in his very provocative book, The Origins of Consciousness in the Breakdown of the Bicameral Mind (1976), notes that there are very few references to consciousness or mental life in early literature (e.g., the Iliad and the Odyssey). To the extent that characters in this ancient literature had thoughts, feelings, and desires, these were not mental acts of the person, but rather things put into his or her mind by the gods.
Around the 6th century BCE, things began to change. Characteristic of the philosophical tradition of the "Golden Age" of Greece (Socrates, c. 469-399 BCE; Plato, c. 427-347; Aristotle, 384-322 BC) was the recognition that people's thoughts, feelings, and desires were their own. This is the origin of consciousness to which Jaynes refers -- the point at which people became aware of the contents of their own minds as such, and also aware of their ability to control these contents themselves. Similar things were happening in Eastern philosophy, by the way: for example, Buddha taught that ideas came from sensations, while Confucius taught that individuals could think for themselves. These were novel, revolutionary ideas at the time.
This philosophical tradition developed further in the West -- first in the hands of certain philosophers of the medieval Christian Church (e.g., Augustine of Hippo, 354-430; Thomas Aquinas, 1225-1274), and later by the philosophers associated with the Enlightenment of 17th and 18th century Europe. The Enlightenment philosophers were particularly interested in the debate over the relation between knowledge and experience. On this question, there merged two fundamental points of view which still divide philosophers, and psychologists, today.
- The rational tradition, also known as nativism, promoted by Rene Descartes (1596-1650) and Kant, taught that at least some knowledge was independent of experience.
- By contrast, the empiricist tradition associated with John Locke (1632-1704), David Hume (1711-1776), and George Berkeley (1685-1753) taught that all knowledge comes through experience.
For highly readable introductions to Enlightenment philosophy, see:
- The Story of Philosophy: The Lives and Opinions of the Greater Philosophers by Will Durant (1st Ed., 1926; 2nd Ed., 1962). This is the classic one-volume history of philosophy -- and you've gotta love the subtitle.
- The Dream of Enlightenment: The Rise of Modern Philosophy (2016) by Anthony Gottlieb, the second volume in his history of philosophy (the first volume, the Dream of Reason, covers the period from the ancient Greeks to the Renaissance).
These and other Enlightenment philosophers posed questions that psychologists now try to settle scientifically, and we will talk about them from time to time in this course. But the Enlightenment philosophers were not ready to pursue a science of mental life. In large part, we owe this reluctance to the doctrine of dualism proposed by Descartes at the very beginning of the Enlightenment period. Descartes held that mind and body were different substances. For example, in contrast to the body, the mind occupied no space. Thus, the argument went, the mind can't be measured; and because science depends on measurement, a science of the mind was impossible.
This position was undercut in the 19th
century, with the development of classical psychophysics.
Ernst Weber (1840) and Gustav Fechner (1860) measured the
relations between physical stimuli and the corresponding sensory
experience -- demonstrating, in the process, that sensory
experience was not only measurable but lawful. At roughly the
same time, Hermann von Helmholtz (1856-1966) was conducting
experimental investigations into the mechanisms of spatial
In addition, Franciscus Donders (1868) showed that mental processing could be measured in terms of the time it takes a person to perform a mental operation -- introducing the reaction time or response latency methodology which forms such an important part of modern scientific psychology.
Similar methods were eventually applied to the so-called "higher" mental processes -- including memory, thought, and any other mental function that went beyond immediate sensory-perceptual experience. For example, Hermann Ebbinghaus (1885) invented the nonsense syllable (strings of letters consisting of a consonant, a vowel, and a consonant, such as TUL, that are pronounceable but meaningless) in order to study the formation of associations between ideas -- and, in the process, showed quantitatively how memory was related to experience. At about the same time, Mary Whiton Calkins (1896), invented the paired associate technique, consisting of one nonsense syllable paired with another, to the same purpose. Ivan Pavlov (1898), a physiologist working in Russia, and Edward L. Thorndike (1898), a psychologist working in the United States, pioneered the study of learning in animals. In this way, in the latter quarter of the 19th century, a science of the mind began to emerge.
In the 20th century, psychology broke away from both philosophy and physiology, and established itself as an independent science. For most of this century, psychological and philosophical analyses of mind proceeded somewhat independently. This was partly due to the so-called "behaviorist revolution" in psychology, which began in the late teens and 1920s. The behaviorists, as their very name implies, studiously avoided any reference to mental states (because they can't be publicly observed), and confined their analyses to tracing the relations between observable physical stimuli, and observable behavioral responses.
But questions about mental life didn't go away. They returned to the forefront in the 1950s and 1960s, when the so-called "cognitive revolution" reinstated mind as a -- some would say the -- proper subject matter for psychology. Now, psychologists and philosophers work together, along with linguists, computer scientists, neurologists, and anthropologists, in the interdisciplinary field known as cognitive science.
The Relation of Psychology to Philosophy
Modern philosophy can be divided into four main branches. Logic is concerned with the formal principles of reasoning, and the criteria by which judgments and inferences are to be held valid. Aesthetics has to do with the nature of beauty and art. Ethics has to do with questions of good and evil, moral duty, and obligation. Metaphysics has to do with the fundamental nature of being and reality.
Metaphysics, in turn, has three main branches: ontology, which is concerned with the nature of existence; cosmology, which is concerned with the nature of the universe; and epistemology, which is concerned with the nature of knowledge.
Each of these branches of philosophy has is psychological counterpart.
- Obviously, logic and epistemology are closely related to psychology as a cognitive science, because both are concerned with the nature of knowledge, and how knowledge is acquired, represented, and used.
- Ethics relates more to psychology as a social science, because both are concerned with the relations between individuals and groups; cognitive psychologists also study the processes by which we make judgments about what is good and what is just.
- Aesthetics also has a cognitive component to it, because beauty is something which is perceived; but also a social component, as the standards for beauty and artistic character vary from time to time and place to place.
In addressing questions of mind (or, for that matter, any other question), philosophers use three main methods: introspection, or the detailed inquiry into their own experiences and beliefs; linguistic analysis, or the meanings of words and the ways in which they are used in language; and logical argument, based on principles developed in the study of rational judgment.
There is much to be gained by such efforts. However, even philosophers realize that they are not necessarily adequate to the task of understanding and explanation. In the first place, introspection can be biased by inaccuracies and distortion in perception and memory. Moreover, introspection can only reveal what is consciously accessible, not what might be going on outside of phenomenal awareness. Moreover, there is a difference between the principles that might be postulated on the basis of philosophical principle and those that actually govern human experience, thought, and action. For example, philosophers sometimes assume that people follow the principles of normative rationality when making judgments. That is, they engage in careful calculation of probabilities, according to mathematical logic. However, people are generally poor judges of the probabilities of events. To take another example, philosophers sometimes assume that people follow a principle of utilitarianism in their behavior, maximizing pleasure and minimizing pain; but this tendency is reversed in individuals who are depressed or masochistic.
Like the universe as a whole, the mind
cannot be understood by thought and reason alone. Just as
astronomers ask empirical questions about cosmology with the
tools of their science, so do psychologists ask empirical
questions about the mind. The characteristic features of the
scientific method in psychology are the systematic
observation of events under controlled
conditions; observations are collected in formal
experiments which test explicit hypotheses
derived from some theory; observations derived
from these experiments are expressed in quantitative
terms, which are then subjected to statistical tests
to determine the validity of the investigator's inferences. For
more details, see the corresponding Lecture Supplement, "Beyond
Impressions: Descriptive and Inferential Statistics".
The Essence of Science
The essential methods of
science, whether it's a science like physics or a science like
psychology (or, for that matter, a science like sociology) began
to emerge about 1000 years ago. In fact, one writer has called
the scientific method "The Best Idea of the Millennium" ("Eyes
Wide Open" by Richard Powers, 04/18/99). Here's a capsule
history of the development of the scientific method, partly
inspired by Powers' article.
For a more thorough analysis of the scientific method, see The Scientific Method: An Evolution of Thinking from Darwin to Dewey by Henry M Cowles (2020). The essence of the scientific method is often presented as a sequence of five steps: observation, hypothesis, prediction, experiment, confirmation. But as Jessica Riskin, a historian of science at Stanford University, points out in her review of Cowles's book, you could make a reasonable case for almost any of the 120 permutations of these five steps ("Just Use Your Thinking Pump", New York Review of Books, 07/02/2020). Although the scientific method can be traced back to Bacon and Newton in the 17th century, the term "scientist" itself is very young, having been introduced only in 1834 by William Whewell -- and it didn't catch on until much later in the 19th century (the British Association for the Advancement of Science was founded only in 1831; before that). Before that, people like Newton and Galileo, and even Darwin, thought of themselves as natural philosophers, and if British natural philosophers were really famous they were members of The Royal Society for Improving Natural Knowledge, which received its royal warrant in 1663. Cowles concludes that "The rise of 'the scientific method' was less a success than a tragedy", because its "monopolistic claim on transcendent truth" (Riskin's words) set science apart from the humanities.
The Shift from Authority and Intuition to Observation
The Enlightenment of the 17th
and 18th centuries gave rise to a Scientific Revolution in which
divine revelation and arguments from authority and intuition
were supplanted by the search for universal principles through
systematic observation, controlled experimentation, and the
mathematization of universal laws (think of Galileo and Newton).
Islam and the Scientific Revolution
Abu-Ali Al-Hasan Ibn al-Haythem (known in the West as Alhazen), an Islamic scholar born c. 965 AD in Basra (then a city in Persia, now a city in Iraq) and died c. 1040 in Cairo, Egypt, resolved a dispute that was itself almost a century old about the nature of vision. Euclid, Ptolemy, and other ancient authorities had argued from reason that light radiated from the eye, and fell on objects, allowing them to be seen. Aristotle, in contrast, argued that light was radiated by objects and fell on the eye. Both had perfectly reasonable arguments favoring their views, but nobody adduced any evidence for them (Bertrand Russell somewhere noted that Aristotle held the view that women had fewer teeth than men; although he was married twice, it apparently never occurred to him to look in either wife's mouth to see if this was true). Alhazen performed the following simple experiment (among others): he asked observers simply to look at the sun, which burned their eyes (so don't try this at home!). This simple experiment demonstrated conclusively that light was radiated (emitted or reflected) by objects, not by the eyes.
Alhazen's treatise on optics was translated into Latin in the 13th century, as part of the revival of interest in ancient learning known as scholasticism. European appreciation of his work on the geometry of vision led eventually to the invention of techniques for visual perspective in painting, pioneered by the Italian artist Giotto (1267-1337). In recognition of his achievements in mathematics and physics, a crater on the Moon is named in his honor. But for our purposes Alhazen's most important contribution was his appeal to empirical evidence, rather than to authority, abstract theory, or rational argument, to settle disputes about the nature of the world.
Roger Bacon (1214-1294), an
English scholastic philosopher, read Alhazen's work in
translation, and developed his point of view into a full-blown
philosophy of science based on empirical evidence derived from
controlled experiments, in which variables are manipulated one
at a time to see which have an effect on some outcome. Aristotle
had argued against such experiments, on the ground that the
world must be understood as a whole, not in terms of
particulars. In his Opus Majux (1267), Bacon discussed
four causes of ignorance:
- appeals to incompetent authority;
- influence of custom;
- opinions of the ignorant crowd;
- displays of wisdom that cover up what we don't know.
Vaccines and Autism: A Case Study in Bad Science
McCarthy's alarm, in turn, was stimulated by a 1998 paper by Wakefield et al. published in Lancet, a leading British medical journal. They reported 12 children "with a history of normal development followed by a loss of acquired skills, including language", and various gastrointestinal problems. Nine of the children were subsequently diagnosed with autism, one as psychotic, and two with encephalitis. All had received the measles-mumps-rubella (MMR) vaccine. On the basis of these cases, Wakefield et al. suggested that "there is a causal link between measles, mumps, and rubella vaccine" and autism.
The first thing to say is that subsequent research, with a larger group of subjects, has shown no association between the MMR vaccine and autism (or any other neurodevelopmental disorder). None. Nil. Nada. Zip. Zilch. The definitive study was reported by Jain et al,. (JAMA, 2015), based on a database of 34 million people enrolled in American health insurance plans. They classified 95,727 children as to whether they received the MMR vaccine or not, how many doses of the vaccine they received, and whether or not they had an older sibling with autism, and then looked at the incidence of autism. Having received the MMR vaccine had no effect on the risk of autism -- even among children with an older sibling who had the diagnosis, who therefore were at higher risk for autism to begin with. There's just nothing there.
That's how science is supposed to go, as we refine our understanding. All well and good, but (and it's a big "but") the Wakefield study should never have been published in the first place. Why? Because it lacked even elementary controls.
If we want to say that the MMR vaccine causes autism, we need to to take one group of children who got the MMR vaccine, and another group -- a control group -- who didn't, and compare their rates of autism. That's the sort of thing that was done in the followup studies, to disprove the idea that there is any association between the vaccine and the illness. None. Nil. Nada. Zip. Zilch. Wakefield et al. didn't even try to evaluate a control group. They just found 12 kids with a particular syndrome, noted that they had all received the MMR vaccine -- not too surprising, if you think about it, since almost every child in the US and the UK receives the vaccine, and then concluded -- not just erroneously, but illegitimately -- that there might be a causal link between the one and the other.
In the aftermath of the Wakefield publication, enough problems were found with the study (long story, and irrelevant to the point I'm making here) to warrant its retraction -- a relatively rare event in science. The Editor of Nature declared the study fraudulent, not just wrong, and retracted it; 10 of Wakefield's 12 co-authors disavowed the paper; Wakefield himself lost both his academic affiliation and his license to practice medicine. So, science corrected itself.
But the point here is that the absence of even an elementary comparison group -- never mind the absence of a representative sample of vaccinated children -- means that there never was any valid scientific evidence for an association between MMR and autism. Which means, in turn, that the study should never have been published in the first place.
Why the Wakefield study was published, given these elementary considerations, is something of a puzzle, and the fact that it was ever published in the first place is something of a scandal. There were clearly major failures in editorial handling of the manuscript. But the bottom line is this: you can't make claims that X causes Y, or even that X is associated with Y, without a proper control or comparison group.
William of Ockham
(1290-1349), another English scholastic, promoted another
scientific principle, which has come to be known as the Law
of Parsimony, or "Ockham's Razor". Given a number
of different explanations for a particular outcome, Ockham
argued, the simplest explanation is to be preferred over more
complicated ones. Ockham fully realized that the universe might
be very complex; what he argued against was unnecessary
With the principles of
empirical observation, controlled experiment, and parsimony in
hand, the stage was set for the revolution in "experimental
philosophy" announced by Francis Bacon (1561-1626; apparently no
relation to Roger), another English philosopher. In summing up
the scientific method, Bacon sought to banish the four "idols of
- the idols of the tribe, or perceptual illusions;
- the idols of the cave, or personal biases;
- the idols of the marketplace, or linguistic confusions;
- the idols of the theater, or philosophical dogma.
The new science was
exemplified by Galileo Galilei (1564-1642), who used the
telescope to confirm Copernicus' theory that the Earth revolved
around the Sun; William Gilbert (1540-1603), who discovered
magnetism; Johannes Kepler (1571-1630), who discovered that the
planets travel in elliptical, not circular, paths; and William
Harvey (1578-1657), who discovered the circulation of the blood.
Utility of Knowledge
These facts revealed by the
new experimental philosophy were all very interesting, if at the
time they were not particularly useful. But Francis Bacon also
promoted the notion of practical knowledge -- the use of
scientific knowledge to improve the condition of mankind. From
Bacon we get the idea that "knowledge is power"-- an idea
that lies at the heart of our post-industrial "knowledge
economy" based on information and information services. But we
wouldn't get there for a long time (first we had to have an
Francis Bacon also held the
view that science progresses by the steady accumulation of
empirical facts derived from empirical observation. In this inductive
method, facts come first, and theory comes later, induced
from the facts, and explaining the facts. To have a theory first
smacked of the argument from authority or intuition that both
Bacons, Roger and Francis, fought against. Facts, impartially
collected, would speak for themselves. Once a theory emerged
from the data, however, it was never taken as the last word. It
was always subject to continued verification by new
evidence, which would confirm or deny it.
The Hypothetico-Deductive Method
The Baconian emphasis on observation and induction lasted through the 19th century, and well into the 20th. For example, Charles Darwin ((1809-1882) induced the theory of evolution by natural selection from observations of the geographical distribution of finch beaks and tortoise shells. But in the 20th century, Karl Popper (1902-1994) convincingly argued that induction was insufficient to guarantee true knowledge. To use his example, if all you observe are white swans, you might well conclude that all swans are white, but this conclusion would be disproved by the observation of even a single black swan. Accordingly, Popper argued that science should employ a strategy of falsification, seeking evidence that would disprove a hypothesis. Scientific theories generate specific hypotheses, which are tested against data generated by experiments designed to show that those hypotheses are false. The best hypothesis is the one left standing after all the alternatives have been disconfirmed. For Popper, the difference between a genuine science, like physics, and a pseudoscience, like Marxian economics or Freudian psychoanalysis, is that the propositions of physics can be falsified, while those of psychoanalysis cannot. Popper's arguments for falsification rather than verification won the day, and the logic -- or at least the rhetoric -- of falsification is part of the everyday rhetoric of science.
Popper applied this
methodology even to politics, in his book The Open Society.
For Popper, as Colin McGinn put it, science was the model for
civilization ("Looking for a Black Swan", New York Review
of Books, 11/21/02). Given the evidence of his posthumous
collection of essays, All Life Is Problem Solving, it
was also the model for life. For Popper, even elementary
instances of learning consisted in the generation of a
hypothesis, in the form of an expectation, followed by an
empirical test of that hypothesis, until the organism settles on
a hypothesis that cannot be falsified.
Lately, the proliferation of the Internet and social networking has led to the rise of a new movement in the social sciences known as "Big Data", involving data sets containing thousands of variables from millions of subjects. These data sets are then analyzed, mostly by variants of the correlation coefficient, to reveal whatever relationships may exist in the data. For the most part, the analysis of Big Data is entirely inductive. That is to say, the analysts do not approach the data with any specific hypothesis in mind, but rather, seek only to explore it to identify any relationships that exist. As with any exploratory data analysis, the results should not be taken at face value: if p is set at .05, then 5% of the relationships will be "significant" just by chance. Accordingly, some way has to be found to replicate the analyses -- perhaps by splitting the sample in half and determining whether any relationships observed in one half are also observed in the other half, a procedure known as double cross-validation.
The hazards of a reliance on Big Data was nicely illustrated by an article by Seth Stephens-Davidowitz, an economist, who analyzed the Google database for searches related to depression ("Dr. Google Will See You Now", New York Times, 08/11/2013). He uncovered a number of potentially meaningful patterns. For example, searches increase in frequency during the winter and decrease during the summer, and suggested that people prone to depression should consider moving someplace warm. Cute, but in fact, epidemiological data shows that the incidence of depression in Minnesota and Wisconsin is actually lower than that in Alabama and Mississippi. Moreover, the result obscures a more important finding, of seasonal affective disorder, a form of depression already well known to psychiatrists. "Big Data" is, essentially, correlational in nature, and correlation is not causation. Warmth doesn't protect against depression: sunlight does; and it only protects against some forms of depression. But we'd never know this from an analysis of Google searches; we only know this from careful epidemiological research that tests specific hypotheses.
Science and Democracy
Robert Lawrence Kuhn, host of Closer to Truth: Science, Meaning, and the Future, a PBS television series on science, has argued that "scientific literacy energizes democracy", by fostering a stance of critical thinking, including demanding both evidence for claims made by authorities and political elites, and logical reasoning from evidence to conclusions "Critical thinking is the essence of the scientific method. Knowing the difference between assumption and deduction, and between presumption and proof, can alter one's outlook and transform an electorate. Moreover, Kuhn argues, scientific thinking fosters diversity through "the capacity to respect pluralistic political positions -- the essence of democracy -- since members can understand that no position, not even their own, can be 'proved' to be the correct one with anywhere near absolute certainty" ("Science as Democratizer", American Scientist, 09-10/03).
As Dennis Overbye has written ("Elevating Science, Elevating Democracy", New York Times, 01/27/2009):
The knock on science from its cultural and religious critics is that it is arrogant and materialistic.... Worse, not only does it not provide any values of its own, say its detractors, it also undermines the ones we already have, devaluing anything it can't measure, reducing sunsets to wavelengths and romance to jiggly hormones. It destroys myths and robs the universe of its magic and mystery.
So the story goes.
But this is balderdash. Science is not a monument to received Truth but something that people do to look for truth. That endeavor, which as transformed the world in the last few centuries, does indeed teach values. Those values, among others, are honesty, doubt, respect for evidence, openness, accountability and tolerance and indeed hunger for opposing points of view. These are the unabashedly pragmatic working principles that guide the buzzing, testing, poking, probing, argumentative, gossiping, gadgety, joking, dreaming and tendentious cloud of activity... that is slowly and thoroughly penetrating every nook and cranny of the world....
It is no coincidence that these are the same qualities that make for democracy and that they arose as a collective behavior about the same time that parliamentary democracies were appearing. If there is anything democracy requires and thrives on, it is the willingness to embrace debate and respect one another and the freedom to shun received wisdom. Science and democracy have always been twins.
In 2017, with an American president who routinely lies, misstates facts, and prevaricates, and authorities in some political quarters speak of "personal truth" and "alternative facts", Time magazine ran a cover story asking whether truth itself is dead (04.03/2017). Not necessarily. As Frank Wilczek (a Nobel-laureate theoretical physicist) put it: "science plays a vital role in defining the boundaries of rational discourse" because it is the best way we have of determining what is true and what isn't. ("No, Truth Isn't Dead", Wall Street Journal, 06/24/2017). Wilczek goes on to state that:
In science, the meaning of "truth" is more substantial, and less susceptible to cynical manipulation. Empirical facts -- that is, experienced events -- are the gold standard of truth.... Science builds on experience, using logic and... working assumptions [like Newton's laws of motion and gravity].... Yet a hallmark of science is that we spell out and continually check our assumptions -- and, if necessary, modify them. That discipline keeps science honest, reliable and on-track.... "Truth", in the context of morality, law, and politics, is a very different concept from logical or scientific truth. In those domains, science, with its cautious attitude, can't provide all the answers. Different groups of people make different assumptions, which will sometimes lead to very different conclusions. But when any version of "truth" contradicts scientific truth (let alone empirical truth), sensible people must reject it.
The Cycle of Theory and Evidence
falsification are both forms of empiricism, but Popper reversed
the traditional Baconian position with respect to the relation
between theory and evidence. For Bacon, evidence came first, in
the form of observations, and theory came later, by induction.
For Popper, however, theory comes first: in this way, he is the
culmination of a tradition of rationalism that goes back to Rene
Descartes, a 17th-century French philosopher, who attempted to
derive true knowledge from reason alone (and thus initiated
modern philosophy). The scientist first confronts a problem,
such as why the earth appears to revolve around the sun or why
apples fall off trees. Then, he or she offers a number of
theories, or at least hypotheses, as to which that might be the
case. Then, he or she proceeds to test these hypotheses,
attempting to disconfirm them, and retains as true the one
hypothesis that fails to be disconfirmed. "Truth", however, is
always provisional: some future observation may disconfirm even
this theory. In practice, however, the relation between theory
and hypothesis is more complex than this.
Where do Popper's "problems"
come from? They exist in the form of puzzling observations that
demand some sort of explanation. A lot of scientific research
consists in an investigator publishing an observation, or
conducting an experiment that is less intended to test a
hypothesis than it is to "poke nature and see what happens".
From such observational studies, the investigator may then
suggest a theory, or at least a hypothesis (see below). He or
she may also perform a verificationist test that indicates that
the theory/hypothesis is provisionally true, or at least should
be taken seriously by others. Later, another scientist may
propose a new theory, and perform a falsificationist test that
pits one theory against another. But nobody goes to the trouble
of testing every conceivable hypothesis against data
from an experiment specifically designed to reject that
hypothesis. However much scientists embrace the Popperian logic
of falsificationism at the level of rhetoric, actual
scientific work involves both induction and deduction, both
verification and falsification.
A reliance on empirical
evidence is the defining feature of science -- more so than
controlled exerimentation (evolutionary biologists and
cosmologists don't do it), more so than mathematics (Darwin and
Mendel didn't use any beyond arithmetic). In The
Knowledge Machine (2020), Michael Stevens, asserts the
iron rule of explanation: no matter how appealing a theory
might be on other grounds, scientific theories are validated
only by empirical explanation. Scientists may come up with
their hypotheses in a variety of ways, including intuitive
appeal or mathematical elegance, but when it comes to
testing a hypothesis, the only thing that counts is the data.
By the way, about that word theory. A "theory" is often misinterpreted as mere speculation, as when creationists or proponents of "intelligent design" criticize the theory of evolution as "just a theory". But in science, a theory is an overarching explanatory framework that accounts for a large set of empirical observations, and goes beyond observable facts to make plausible inferences about facts that have not yet been observed. These inferences are hypotheses, and experiments are conducted, one way or another, to reveal new facts that will determine whether these hypotheses are correct. Evolution by natural selection is a theory. So is general relativity. Theories are never tested whole. Rather, theories generate specific hypotheses, which are then tested against empirical data.
Research unreported is research undone. It is not until scientific findings are made public, so that other investigators can confirm them, and incorporate them into their theories, or refute them (or at least set limits on them), that research is completed. In order to facilitate publication of scientific research, the first scientific journals were founded in the late 17th century -- the Journal des Savants in France (1665), and the Philosophical Transactions of the Royal Society, in England (1667). The first scientific journals devoted to psychology appeared only in the late 19th century:
- Mind (1876), founded by Alexander Bain, published mostly philosophical analyses of mental life, but did publish some psychological work -- notably William James' famous essay on "What is an Emotion?".
- Philosophische Studien (Philosophical Studies, 1881), founded by Wilhelm Wundt primarily to publish studies from his own laboratory (other departments of psychology, including Wisconsin and Berkeley, also sponsored such "house organs").
- American Journal of Psychology (1887), founded by G. Stanley Hall as part of a group of pioneering American scientific journals sponsored by Johns Hopkins University, and intended as an expressly psychological counterpart to Mind.
- Zeitschrift fur Psychologie und Physiologie der Sinnesorgane (Journal for the Psychology and Physiology of the Sense Organs, 1890), founded by Hermann von Ebbinghaus to publish a wider variety of studies than those produced by Wundt's laboratories. In the 19th century, scientific psychology was often referred to as "physiological" psychology, to distinguish it from merely "philosophical" work. Later, the references to "physiology" and the "sense organs" were dropped and the journal was renamed simply the Zeitschrift fur Psychologie.
- Psychological Review (1894), founded by Mark Baldwin and James McKeen Cattell, and now the "jewel in the crown" of the American Psychological Association's publication program.
Publication is an important aspect of the transparency of the scientific method. When scientists report their empirical findings, they also describe the method by which those findings were obtained, so that other scientists can repeat what they have done and confirm or disconfirm their observations. This allows scientists to build on each other's work, so that science is a cumulative enterprise. But this also allows others to critique the experimenter's method, and find flaws that, when corrected, might yield different and more valid results. We do not have to have "been there" when the experiment was done. We can understand, and critique, the experiment solely on the basis of the experimenter's report of his method.
Scientists confirm or disconfirm each other's findings through replication -- that is, one scientist does what another scientist says he did, and sees if she gets the same result. Actually, there are two kinds of replication:
- direct replication, in which the initial study's methods are repeated as precisely as possible;
- conceptual replication, which depart from the original procedure in various ways, to test a hypothesis that is conceptually related to the original.
Even direct replications are never precisely identical to the original. An experiment conducted on subjects recruited from Stanford isn't exactly the same as the original conducted on subjects recruited from Berkeley; and one conducted in 2012 may employ subjects who are quite different from those in an original conducted in 1962 -- even if they are all college students. So "replication" is a matter of degree. What is really important is that the replication be faithful to the spirit of the original; and follow the letter of the original as closely as possible.
Beginning in the 2010s, psychology and other fields began to
face a kind of replication crisis -- which is to say, a
number of highly visible experiments failed to be replicated,
casting doubts, not just on the original studies, and the
researchers who conducted them, but also on the field in general
(Pashler & Wagenmakers, 2012).
- In 2014, the Many Labs (ML) project attempted to replicate
13 effects reported in social psychology journals, 11 of which
were successfully replicated (Klein et al., Social
Psychology, 2014). Two effects, which in fact had
aroused controversy when first published, failed to replicate
- In 2015, the Open Science Collaboration (OSC; Science,
2015) reported the results of 100 attempts to replicate
effects reported in 2008 in three prominent psychology
journals, representing a wider sample of psychological
research. Only 47% of the replications were deemed
successful, in that they yielded statistically significant
effects similar to the originals.
At first glance, however, the outcome of the OSC study would
seem to impeach the validity of much psychological research, if
not psychology in general, but this would be misleading (as
noted by Gilbert et al., Science, 2016). For
example, some of the "replications" weren't true replications,
in that they departed significantly from the procedures of the
original study. For example, one study of white Americans'
stereotypes concerning African-Americans was "replicated" in
Italy. And a study which asked Israelis to imagine the
consequences of military service was "replicated" by asking
Americans to imagine the consequences of a honeymoon.
These procedural infidelities also occurred in some of the ML
"replications" as well. In fact, replications whose
procedures were endorsed by the authors of the original study
succeeded 60% of the time, compared to 15% of studies which were
Still, 60% isn't a great hit rate, either, and does suggest
that psychology does faces a kind of replication crisis.
From roughly the time of
Roger Bacon onward, science has been concerned with
understanding the natural world of physics and biology. Under
the influence of Descartes' distinction between mind and body,
the 18th-century German philosopher Immanuel Kant asserted that
there could never be a science of the mind, because the mind was
not a physical entity that could be measured. It was not until
the mid-19th century that Weber, Fechner, Helmholtz, and other psychophysicists
showed that "lower" mental processes such as sensation and
perception could be subject to scientific analysis, and only in
the late 19th century that Ebbinghaus and others showed that the
same was true for "higher" mental processes such as memory. Also
in the mid-19th century, August Comte (1798-1857), a French
philosopher, showed that science could reveal the workings of
social groups as well as the workings of the individual mind.
Based as they are on controlled observation and the testing of
hypotheses derived from theory, the "social" sciences of
sociology, anthropology, economics, and political science are
every bit as much sciences as are the "natural" sciences like
physics, chemistry, and biology.
Some philosophers of science
have claimed that social science can't be real science
because it isn't predictive; it can only explain things that
happened, in a post-hoc manner. The sciences are real
sciences, because they entail testing predictions in
experiments. This claim is bogus.
- In the first place, there are plenty of natural sciences
that explain, but cannot predict. Seismology and
meteorology are the classic examples: earth scientists can't
predict earthquakes or tornadoes, but they have a very good
understanding of how they happen.
- And while it's true that we can't manipulate the features
of whole societies in order to do experiments, we can gain
predictive knowledge by conducting smaller-scale
experiments, as social psychologists (and some sociologists)
do. Lots of economists -- just not Alan Greenspan, the
Chairman of the Federal Reserve, and his company of
neoclassical True Believers -- predicted the financial
crisis of 2008.
The real difference between the natural and social sciences is that the phenomena of natural science are observer-independent. Galaxies, tectonic shifts, and hurricanes exist regardless of whether there is anyone to observe them. But the phenomena of social science are different, because they are observer-dependent: they are the product of human cognitive activity -- of consciousness, if you will. They don't exist unless there is an observer present to experience -- and construct -- them. Mountains and molecules have features that are intrinsic to their physics. But marriage and money depend for their existence on human attitudes: they are what they are only by virtue of agreement between conscious beings.
In this respect, economics
may be an intermediate case. When Adam Smith, in The
Wealth of Nations (1776), referred to the "invisible
hand", he seemed to imply that the laws of economics -- of
supply and demand and so forth -- are observer-independent
phenomena that occur regardless of human cognitive
activity. But many of the facts of economics are
observer-dependent. Like currency: a dollar bill is worth
a dollar only because someone says it is; as a piece of paper,
it has no intrinsic, observer-independent value. And
markets: you can have a capitalist economy, or a socialist
economy, or a mixed economy, etc.; one economic system may be
better than another, what economy you have depends on someone's
choice. Capitalism isn't in physics.
For a provocative discussion of the status of economics as a science -- a discussion that has implications for psychology -- see:
- "What Is Economics Good For?" by Alex Rosenberg and Tyler Curtain (New York Times, 08/25/2013).
- "Economics as Science" by Eric S. Maskin (New York Times, 08/29/2013),
- and the dialogue stirred by Maskin's letter (New York times, 09/01/2013).
And for that matter,
psychology may also be an intermediate case, because it is both
a biological science, interested in the relations between mental
states and brain activity, and a social science, interested in
the relations between mental structures and processes and social
structures and processes. (Psychology is primarily a
social science, though, because it is fundamentally concerned
with the individual's mental life: his or her knowledge and
beliefs, feelings and desires.)
- As a natural science, psychology is concerned with discovering universal laws like the psychophysical laws, or George Miller's "magical number 7, plus or minus two". But even these laws are observer-dependent, because they wouldn't be true in the absence of an observer.
- As a social science, psychology is concerned with how the thoughts, feelings, and desires of the individual relate to what is going on in the world around him -- a world that is very much a social world created by human minds.
In the final analysis,
however, both economics and psychology are social sciences,
because the phenomena they study are essentially human
constructions, and their processes can be altered by the very
predictions that social scientists make.
- The financial crisis of 2008 might have been averted if policymakers had listened to dissident economists, and enforced stricter regular on the financial-services industry.
- If I predict, based on your prior test scores, that you'll get a poor grade in Psychology 1, you might study harder just to prove me wrong.
Both cases differ from the natural sciences. In seismology and meteorology, predicting an earthquake doesn't make it happen; and if a hurricane is predicted, nothing can be done to prevent its formation. That's because earthquakes and hurricanes are observer-independent phenomena. Financial crises, and individual choices, aren't.
Psychology (on its "social"
side) and the other social sciences are sometimes characterized
as "soft science", in contrast to allegedly "hard"
sciences like physics and chemistry. But that's a
misnomer. As Theodore Lowi, a prominent political scientist,
once remarked, "political science is a harder science than the
so-called hard sciences because we confront an unnatural
universe that requires judgment and evaluation". The same
is true for psychology as a social science.
Well into the 20th century,
most science was done by individual investigators, often
independently wealthy or supported by wealthy patrons. Galileo
essentially worked alone; so did Darwin and the Curies. But in
the 1930s and 1940s, and especially with the Manhattan Project
to build the atomic bomb during World War II, all that changed:
now much science is was done by large teams of investigators
supported by large government grants. This is certainly true in
physics and astronomy, where research into the smallest and
largest domains of the universe is conducted enterprises like
the Lawrence Berkeley Laboratory (the first national laboratory,
was founded by E.O. Lawrence in 1931) using instruments like the
Hubble Space Telescope and the proposed Superconducting
Supercollider. In biology there is the Human Genome Project, and
in medicine there are multi-site clinical trials and large-scale
Psychology is also entering
into a phase of Big Science, with brain-imaging studies that
require whole teams of investigators to carry out -- not to
mention "Big Data" based on huge numbers of observations
culled from the Internet. Still, even in astronomy, the oldest
and most developed of the sciences, there is room for
small-scale and even amateur researchers ("In Praise of
Amateurs" by Freeman J. Dyson, New York Review of Books,
12/05/02). In psychology, an lone investigator, armed only with
a paper-and-pencil questionnaire, desktop computer, and a bunch
of willing college students, can make fundamental contributions
to the field.
Big Science. Yodellayheehoo
(Laurie Anderson, "Big Science" from United States I-IV, 1983)
The Experimenting Society
Science comes in two forms,
basic, interested in knowledge for its own sake, and applied,
interested in the application of scientific knowledge to improve
human affairs. In the 1960s, the psychologist D.T. Campbell and
others proposed that the scientific method be applied to
questions of public policy as well as to questions of scientific
theory. In this way, public policies could be freed from
ideology, and put on an objective, scientific basis. If you
think that vouchers improve educational outcomes of inner-city
schoolchildren, or that managed care improves the quality of
healthcare while lowering its cost, then do the experiment
and find out.
Science is concerned with
causal explanation -- not just with describing the universe, but
also with explaining how it came to be that way. And since
roughly the time of Aristotle, our concept of causation has been
unidirectional: A affects B, which in turn affects C. However,
it's now clear that, in both the natural and social sciences,
causality can be bidirectional or reciprocal: A
can have an effect on B, but B can also have an effect on A
while C can affect both B and A. A situation where everything
affects everything else -- or at least could -- calls
for a new set of scientific methods. To a great extent, this is
what theories of chaos or complexity are all
From roughly the time of
Roger Bacon onward, the prevailing view of scientific progress
is of an incremental, successive, approximation to the truth. We
start out with a pretty good theory, which gets refined by more
rigorous experiments -- or gets rejected when those experiments
fail. Theories are accepted because they have the best evidence
supporting them. But in the 1960s, Thomas Kuhn, a philosopher of
science trained in physics, argued that that's not how science
works at all. From Kuhn's perspective, the competition between
theories is essentially a political battle. At any one time,
scientific investigation proceeds within a generally accepted
view of the world, which Kuhn calls a paradigm, which
determines which questions get asked and how they get answered.
Knowledge builds up within this paradigm, which Kuhn calls "normal
science", until a point comes when research reveals
certain anomalous results, which cannot be explained
within that framework. At that point a new paradigm emerges,
which explains the anomalous results as well as all the results
that were consistent with the old paradigm emerges. Kuhn
characterizes the competition between the new paradigm and the
old one as a period of revolutionary science.
Eventually, the new paradigm triumphs over the old one, an event
which Kuhn calls a paradigm shift. The Copernican
revolution in physics was one such scientific revolution; so was
the Darwinian revolution in biology; the rise of chaos and
complexity theory may also reflect a paradigm shift.
From roughly the time of
Roger Bacon onward, and particularly after Descartes, Western
culture has been based on the view that true knowledge can be
obtained by observation and reason -- a human-centered view of
things known as modernism. However, Kuhn's notion of
scientific revolutions implies that scientific revolutions are
won and lost not by the data, but by an essentially political
process. In his view, scientific revolutions occur not because
the new paradigm is empirically better than the old one, but
because the proponents of the new paradigm achieve positions of
power within the discipline. This means that you can have not
just a philosophy of science and a history of science, but also
a social science of science, which seeks to understand
how scientific research is shaped and constrained by social
forces. A lot of scientists don't like this view, because they
think that "true" science is objective, and thus independent of
socio-political influence. Still, there's something charming
about skepticism, which has been at the center of science since
the time of Roger Bacon, being applied to science itself. At
their core, for all the occasional silliness about physical laws
being social constructions, that is what science studies are all
Some social theorists have also taken
Kuhn's view to mean that science does not really entail a
progressive, successive approximation to truth, but that the
various paradigms are each true in their own way --
or, to put it differently, that there are many truths, all
equally valid. This is essentially the viewpoint of postmodernism,
or post-structuralism. Although postmodernism would seem
to be essentially anti-scientific, this is only true when
science is confined to the physical and biological spheres. If
you jump off a building, you're going to fall no matter what you
believe. This is because the Law of Gravity is the same for
everyone. But postmodernism has some virtues when applied in the
social sciences, because some reality is, in fact, socially
constructed. To take a clear example, a dollar bill is worth a
dollar for no other reason than that the American government
says it is. Many human institutions are purely social
constructions, but they are no less "real" because of that fact.
Scientific evidence, such as
fingerprints and DNA assays, is often used in the courtroom to
provide evidence of guilt or innocence. Under the traditional Frye
Rule (1928), scientific evidence was admissible if
the principle in question -- that fingerprints or DNA are
unique, for example -- was generally accepted within the
relevant scientific community. But in its 1993 Daubert
decision, the Supreme Court left it to individual judges
to determine whether a claim is adequately supported by the
available scientific evidence. Most judges are not trained
scientists, of course, and so the Daubert decision
left the problem of distinguishing between genuine and bogus
science. Robert L. Park, a physicist, addressed this issue in
his book, Voodoo Science: The Road from Foolishness to
Fraud (2002). According to Park, here are "The Seven
Warning Signs of Bogus Science" (Chronicle of Higher
- The discoverer pitches the claim directly to the media, instead of undergoing peer review.
- The discoverer says that a powerful establishment is trying to suppress his or her work, effectively discounting critiques by mainstream scientists.
- The scientific effect involved is always at the very limit of detection (the better the experiment, the higher the signal-to-noise ratio).
- Evidence for a discovery is anecdotal instead of emerging from controlled experiments.
- The discoverer says a belief is credible because it has endured for centuries, even if modern scientific evidence contradicts the belief.
- The discoverer has worked in isolation, instead of being part of a community of scientists.
- The discoverer must propose new laws of nature to explain an observation, instead of discounting observations that are inconsistent with established scientific laws.
Ethics in Research
No matter how interesting or important the question, there are certain studies that scientists simply can't perform, because they're unethical. Ever since the trial of the "Nazi Doctors" following World War II, international law has recognized that the procedures employed scientific and medical research, including psychological research, must conform ti certain ethical standards. The standards differ somewhat for basic and applied (medical and psychotherapeutic) research, but the basic principles are these:
- Subjects must give informed consent to participate in research.
- Insofar as this is possible, investigators must take care to
eliminate any risk that subjects will be harmed by their
participation in any research study.
- "Risk" is defined broadly to include not just physical risks, but also psychosocial risks -- e.g., threats to self-esteem or psychological well-being, or harm to a social group of which the subject is a member.
- Any such risks must be clearly explained to subjects before they agree to participate in the study.
- To insure compliance, proposed research must be evaluated
and approved by an Institutional Review Board (IRB) with the
authority to deny permission to an investigator to conduct the
study in question.
For background on the ethics of human research, particularly medical research, see a pair of articles by Marcia Angell, former Editor of the New England Journal of Medicine, published in the New York Review of Books:
- "Medical Research: The Dangers to the Human Subjects" (11/19/2015).
- "Medical Research on Humans: Making It Ethical" (12/03/2015).
Angell traces the deep background of research ethics, beginning with the Nuremberg Code issued in 1947, and subsequent developments, such as the 1964 Declaration of Helsinki published by the World Medical Association and the Common rule issued by the US Department of health and Human Services in 1991, and also discusses more recent cases. Angell is a physician, so most of her discussion is focused on medical research, such as the ethics of placebo-controlled studies. But her general points are applicable to psychological and other behavioral-science research as well.
One important difference between basic psychological research,
and applied medical and psychotherapeutic research, is that the
"subjects" in applied research are often patients seeking
treatment for some illness or disease (such as cancer or
schizophrenia), and they often volunteer for research (such as
clinical trials) in the hope that they will receive effective
treatment for whatever their illness is. Insofar as basic
psychological research is concerned, the primary rule is that
psychological experiments are "episodic". That is,
there is the assumption that the subjects who participate in
them will not be changed by virtue of their participation.
They might be a little richer, by virtue of compensation for
their participation, and they might be a little more
knowledgeable about some aspect of psychology; but they'll leave
the experiment "the same person" as they were when they arrived.
Where Psychology Fits
Because the brain is the
physical basis of mind, psychology is a natural science, closely
tied to biology. But because human thought and action takes
place in a social context, psychology is also a social science.
In some sense, psychology links the social sciences to the
biological science, through its emphasis on the experience,
thought, and action of the individual human organism. Either
way, psychology is a science, just like biology and sociology.
Social science studies a social reality that may differ from one
society to another, but that doesn't make social science
unscientific. Social scientists share with their colleagues in
the physical sciences the basic Baconian virtues. As Bertrand
Russell put it (somewhere):
It is not what the man of science believes that distinguishes him, but how and why he believes it. His beliefs are tentative, not dogmatic; they are based on evidence, not on authority or intuition."
For more on what science is and what it isn't, how it works and how it doesn't, see UCB's "Understanding Science" website.
A Capsule History of Psychology
The pioneering 19th-century psychologist Herman von Ebbinghaus remarked that
"psychology has a long past, but only a short history".
The "long past" reflects more than 2,500 years of philosophical inquiry into cognition and other matters of mind, going back at least as far as the ancient Greeks. The word psychology is, of course, derived from the Greek psycho, referring to the "soul" or the "mind", and the Latin logia, or "study". The word was first used (in German) to refer to the "study of the soul" or of spirits", as a kind of theological discipline. But by the early 18th century, the German philosopher Christian Wolff was using the term in roughly our modern sense. The word first occurs in English in writing by the British philosopher David Hartley, who defined psychology as "the theory of the human mind", a branch of natural philosophy.
But all of this early psychology was strictly philosophical in nature, based on introspection, reasoning, and logical inference, not on the systematic collection of empirical evidence.
The "short history" is due
to the fact that psychology as a scientific enterprise only
began to develop in the 19th century. Why, if people have been
interested in how their minds work for so long, did psychology
emerge as a science so long after physics, chemistry, biology,
and other natural sciences?
From Philosophical Psychology to Scientific Psychology
In large part, the delay in the emergence of psychology as an independent science is attributable to the French philosopher Rene Descartes (1596-1650), who in the 17th century articulated a philosophical position known as dualism. According to Descartes, body and mind were composed of two different substances, the first material in nature, and the second immaterial. Based on this doctrine of dualism, the 18th-century German philosopher Immanuel Kant argued that psychology could never be a science, because science was based on measurement and the mind, being immaterial, could not be measured. Thus, during the Enlightenment, when other sciences were developing rapidly, psychology was ruled out of the scientific enterprise by definition.
- Ernst Weber (1830) and Gustav Fechner (1860) asked their subjects to assign numbers to the intensity of their sensory experiences, and discovered the first psychophysical laws liking various physical measurements of the stimulus to quantitative aspects of experience.
- Ernst Muller (1833-1840) articulated a Doctrine of Specific Nerve Energies, organizing the modalities of sensation according to the organization of the nervous system, rather than the nature of the stimulus, thus linking mind with body in what came to be known as "physiological" (as opposed to philosophical) psychology.
- Hermann von Helmholtz began his experiments on the perception of distance and depth, resulting in the publication of his Physiological Optics (1856-1867).
- Early physiological psychologists moved beyond psychophysics, employing reaction time to measure the speed of a neural impulse (Helmholtz, 1850) and of mental processes (Donders, 1868).
A Catalog of "Firsts"
At this point, scientific psychology began to develop rapidly
- In 1879, Wilhelm Wundt established the first psychological laboratory at the University of Leipzig.
- The first American psychology laboratory was established at Johns Hopkins University by G. Stanley Hall in 1883.
- Other American laboratories followed quickly thereafter.
- At the University of Pennsylvania, in 1888, by James McKeen Cattell.
- Penn also hosted the first free-standing psychological clinic, founded by Lightner Witmer in 1896 (Witmer also coined the term "clinical psychology").
- At the University of Wisconsin, in 1889, by Joseph Jastrow.
- At Harvard University, in 1891, by Hugo Munsterberg, who had been invited to join the faculty at the instigation of William James, precisely for the purpose of doing so.
Actually, a claim could be made that Harvard had the first psychology laboratory in the world, because James had already installed some laboratory apparatus in the Philosophy Department beginning as early as 1875; but James disliked experimentation, and didn't really go beyond classroom demonstrations to conduct formal experiments; so the honor of the first working American psychology laboratory goes to Hall at Hopkins).
For the first half-century or so, scientific psychology was represented by individual journal articles and specialized monograph studies. Eventually, however, psychologists began to assemble the emerging body of scientific research and theory into comprehensive textbooks.
- Wilhelm Wundt published the first textbook of psychology, the Grundzuge der Psychologie, in 1873-1874.
- In 1890 -- only a century after Kant's pronouncement -- William James published his Principles of Psychology, the first comprehensive textbook summarizing the principles of this new "science of mental life".
Actually, a case can be made that the first comprehensive textbook of psychology, covering cognition and emotion, and including personality and social psychology, was Kant's own Anthropology, which appeared in 1798 (Hatfield, 1798; Kihlstrom, 1998. By "anthropology", Kant meant "knowledge of mankind", which for him included the mind as well as culture. But Kant's book was based on his own personal experience, and rational analysis, not the kind of controlled empirical research represented in Wundt's and James's texts. It is perhaps more properly considered the last textbook of philosophical psychology. But it's an interesting book nonetheless, and well worth dipping into.
First American PhDs
- G. Stanley Hall, who (arguably) founded the first psychological laboratory at Hopkins, had taken his PhD at Harvard under William James in 1878. But because psychology was at the time taught in the Department of Philosophy, Hall's degree was technically in philosophy, not psychology -- though his dissertation did include some experimental work on sensory processes. In fact, Hall's was the first doctoral degree ever awarded by Harvard's philosophy department.
- Joseph Jastrow, who founded the psychology laboratory at Wisconsin, took the first American PhD in psychology in 1884. His advisor was a philosopher, C.S. Peirce, and we'll look at an experiment they did together in the lectures on Perception, and again in the lecture on Consciousness and Unconscious Mental Life.
At first, psychological research was published in journals of philosophy, like Mind, and in general scientific journals, like Nature and Science, but as the literature burgeoned, universities and publishers began to sponsor specialized journals devoted to psychology.
- Despite its title, Philosophische Studien was founded by Wundt in 1881 to publish research emanating from his laboratory at Leipzig.
- The American Journal of Psychology was founded in 1887 by G. Stanley Hall as part of a group of pioneering American scientific journals sponsored by Johns Hopkins University, and intended as an expressly psychological counterpart to Mind, a journal of philosophy.
- In Germany, the Zeitschrift fur Psychologie und
Physiologie der Sinnesorgane ("Journal of the
Psychology and Physiology of the Sense Organs") was founded
in 1890 by Hermann von Ebbinghaus to publish a wider variety
of studies than those produced by Wundt's
- In the 19th century, scientific psychology was often referred to as "physiological" psychology, to distinguish it from merely "philosophical" work. And, for reasons to be discussed later, early scientific psychology focused mostly on problems of sensation and perception. Later, the references to "physiology" and the "sense organs" were dropped and the journal was renamed simply the Zeitschrift for Psychologie.
- The Psychological Review was founded in 1894 by Mark Baldwin and James McKeen Cattell, and is now the "jewel in the crown" of the publication program of the American Psychological Association.
As psychology began to be accepted as a scientific enterprise, psychologists began to organize themselves as an academic discipline.
- The American Psychological Association, founded in 1892 by James and others, serves both scientific and applied psychology.
- The Society of Experimental Psychologists, founded by E.B. Titchener at Cornell in 1904, is a small, highly selective, and very informal "honorary society". The SEP's Warren medal is among the highest honors a psychologist can receive (the other is the Grawemeyer Award in Psychology, administered by the University of Louisville, and often considered psychology's "Nobel Prize"
A Whig History of Scientific Progress in Psychology
In much the same way
that Immanuel Kant believed that scientific psychology was
impossible, Wilhelm Wundt believed that scientific psychology,
while possible, was limited to the study of immediate experience
-- that is, to sensation and perception. This is because
he believed that it was important, scientifically, to tie mental
experience to the physical conditions of stimulation, and to the
physiology of the nervous system. In this view, the
so-called "higher" mental processes, such as memory and thought,
were not susceptible to experimental investigation. They were
too far away, as it were, from the instigating physical
stimulus; and the underlying physiology was to complex.
Accordingly, Wundt distinguished between two kinds of science:
- Naturwissenschaft, a German term meaning "science of nature".
- Geisteswissenschaft, meaning "science of the spirit" -- where "spirit", in this context, refers to so-called "higher" mental processes rather than anything like the soul.
- In Wundt's view, experimental psychology had to be limited to basic mental functions such as sensation and perception, where the stimulus conditions could be tightly controlled and performance was very close to physiology. The rest of psychology could only be analyzed by methods that were more observational, and even historical, in nature -- what Wundt called Volkerpsychologie.
Nevertheless, just as Weber and Fechner proved Kant wrong about measuring the mind, beginning in the 1980s a number of pioneering psychologists about the possibility of investigating "higher" mental processes, increasingly distant from both physical stimuli and physiology.
- The above-mentioned Hermann von Ebbinghaus
(1850-1909) invented the nonsense syllable for in
order to study of the formation of associations between
ideas -- and, in the process, showed quantitatively how
memory was related to experience. Nonsense syllables
are strings of letters consisting of a consonant, a vowel,
and a consonant, such as TUL, which are
pronounceable but meaningless (nonsense syllables are also
sometimes called CVCs). Ebbinghaus measured the
strength of a memory by how long it took him to memorize a
list of nonsense syllables, and showed that memory strength
was related to both the number of times the item was
repeated, and the length of time since it had been
studied. In this way, he did for memory what the
psychophysicists had done for the "lower" mental processes
of sensation and perception -- relate a mental state to the
conditions of stimulation.
- At about the same time, and to the same purpose, Mary Whiton Calkins (1863-1930) invented the paired-associate technique, consisting of one nonsense syllable paired with another.
- In about 1898, both Ivan Pavlov *1849-1936), a physiologist working in Russia, and Edward L. Thorndike (1874-1949), a psychologist working in the United States, pioneered the story of learning in animals -- inventing the paradigms now known, respectively, as classical and instrumental conditioning.
- Early in the 20th century, Clark L. Hull (1884-1952) adapted Ebbinghaus's method to the study of concept learning, conclusively demonstrating that "higher" mental processes beyond memory could be studied quantitatively (Hull, 1920).
Reflecting the concerns of Cartesian "modern" philosophy, most early experimental psychology was focused on knowledge, and the means by which it is acquired through experience -- sensation, perception, learning, memory, and thinking. But experimental psychology also took up the other two aspects of the Kantian trilogy of mind.
- Walter B. Cannon (1915) explored the relations between emotional and motivational states, like fear and hunger, and bodily processes, thus expanding the scope of scientific psychology beyond cognition to the rest of the Kantian trilogy.
- At roughly the same time, a number of scientists began to use the new experimental methodologies to study the nature of mental illness.
- In the 1890s, Emil Kraepelin, a psychiatrist who had studied psychology with Wundt, adapted Donders's reaction-time method to the study of mental patients.
- C.G. Jung, inspired by Sigmund Freud, standardized a method for collecting "free associations" to study individual patterns of thinking.
All of this work was focused on how the mind operates in general -- the basic principles of cognition, emotion, and motivation that apply to everyone. But quite quickly, psychologists began to be interested in individual differences in mental function -- that is, how people might differ from each other.
- The foundations for this work were laid by Friedrich Bessell, a German astronomer who in 1820 discovered that some of his colleagues had faster reaction times then others, leading to inaccuracies in estimating the transit times of stars (necessary for navigation).
- In 1883, Sir Francis Galton, a cousin of Charles Darwin, introduced standardized tests of individual differences in mental functions, based on techniques already developed for the study of sensation and perception. Darwin, of course, had proposed that individual differences were the key to evolution -- some traits were more adaptive than others, and were favored by natural selection. While Darwin focused on physical traits, Galton was interested in mental traits.
- In 1884, Galton introduced mental testing to the public
at the "Anthropometric Laboratory" which he set up at the
International Health Exhibition, in London, in 1884. There
the public could pay to be run through various tests of
their mental faculties -- receiving, in return, a copy of
their test results and comparative information from other
- American psychologists quickly followed suit, in a psychology exhibition at the 1893 Chicago World's Fair.
- In order to manage all the data that he collected at his Anthropometric Laboratory and elsewhere, in 1886 Galton introduced the statistical techniques of correlation and regression analysis, still in use today, for the analysis of individual differences.
- In 1905, Alfred Binet and Theodore Simon, two French psychologists, introduced the first "intelligence tests" for measuring individual differences in mental ability among schoolchildren.
- In 1912, William Stern introduced the notion of the intelligence quotient, or IQ, subsequently refined by the American psychologist David Wechsler.
- Questionnaire methods for assessing individual differences in personality were first developed in 1917 by Robert S. Woodworth, as an aid to personnel selection (otherwise known as the military draft) during World War I.
- In 1931, Robert Bernreuter developed the first multidimensional "personality inventory", measuring several personality characteristics (introversion, dominance, neuroticism, and self-sufficiency) in a single test.
- Louis L. Thurstone and Ernest J. Chave (1929), along with Rensis Likert (1932), subsequently adapted the questionnaire method for the assessment of social attitudes, such as racial prejudice and political liberalism-conservatism.
- In 1898, around the time that Pavlov and Thorndike were engaged in their studies of animal learning, Norman Triplett reported the first experimental study of social influence, thereby proving Wundt to be wrong about social psychology as well.
- Richard LaPiere (1934) conducted a pioneering study of the effects of racial and ethnic attitudes on behavior.
- In 1935, when Muzafer Sherif experimentally studied the effect of social conformity on the autokinetic illusion, the circle was complete: the kinds of experimental techniques that Wundt and the other pioneers had used to study immediate experience (e.g., the perception of motion) were now being used to study personality and social processes as well.
- In the 1890s, Emil Kraepelin, a psychiatrist who had studied psychology with Wundt, adapted Galton's paradigm, along with Donders's reaction-time method, for the experimental study of patients with mental illness.
- In the 1930s, David Shakow established the first American laboratory for experimental psychopathlogy at Worcester State Hospital in Massachusetts.
- Already by 1936, J. McV. Hunt could review some 200
experimental studies of various forms of mental illness.
- Also in the 1930s, Henry Murray and his colleagues, particularly Saul Rosenzweig, employed experimental methods to study the influence of personality on experience, thought, and action.
At this point, by the
mid-1930s, personality and social psychology emerged
full-fledged as a quantitative, experimental science of
individual mental life in its social context.
Schools of Psychology
When scientific psychology began, it was organized into "schools" of investigators who shared certain assumptions and methods (now called paradigms), often centered on particular individuals.
The first of these was structuralism, associated with Wundt at Leipzig, and also with his student, E.B. Titchener, at Cornell. Like Wundt, the structuralists were focused on immediate experience, meaning problems of sensation and perception. They got their name from their assumption that complex experiences could be analyzed into constituent, simple elements -- a kind of mental chemistry.
In the late 19th century, structuralism had its principal American rival functionalism, associated with William James (always at Harvard), John Dewey (first at Chicago, then at Columbia), and James Rowland Angell (first at Yale, then at Chicago). The functionalists were much influenced by Darwin's theory of evolution: whereas for the structuralists mind just existed, as a thing to be analyzed, for the functionalists mind had a purpose -- to aid in adaptation to the environment.
In the early 20th century, a third school, known as behaviorism, sprung up around John B. Watson (at Hopkins), and, later, B.F. Skinner (first at Minnesota and Indiana, and later at Harvard). The behaviorists were troubled by the fact that conscious experience was inherently private, whereas science should be based on public observation. Accordingly, they redefined psychology: it was no longer the science of the mind, as James had defined it, but rather a science of behavior. The behaviorists, as their very name implies, studiously avoided any reference to mental states (because they can't be publicly observed), and confined their analyses to tracing the relations between observable physical stimuli, and observable behavioral responses.
But questions about mental life didn't go away. They returned to the forefront in the 1950s and 1960s, when the so-called "cognitive revolution" overthrew the behaviorist revolution and reinstated mind as a -- some would say the -- proper subject matter for psychology. Cognitive psychology is now central to scientific psychology.
Psychology in Interdisciplinary Inquiry
Psychology is an independent
scientific discipline, derived from neither biology nor
sociology, and that stands at the nexus of the biological and
social sciences. At the same time, psychologists participate in
a number of interdisciplinary fields of inquiry that are
concerned with various aspects of mind and behavior.
Psychology and Cognitive Science
Psychology is a component of a broad interdisciplinary field known as cognitive science, which takes as its subject matter the acquisition, representation, and use of knowledge by minds and brains, machines and societies. The various fields in cognitive science are represented by the "cognitive hexagon" presented in a report to the Sloan Foundation, which provided early financial support to various academic programs in cognitive science, including the one at Berkeley:
- As noted earlier, philosophy has a long record of trying to understand the nature of knowledge and knowing. As Howard Gardner (1985) has put it, "Philosophy asks the questions and checks the answers".
- Psychology provides a broad range of experimental
methods for understanding cognitive processes in humans and
other animals, as well as a rich body of empirically based
theory concerning various aspects of cognition.
- Linguistics provides specialized methods and theories concerning the nature of language.
- Neuroscience provides an understanding of the brain as the physical basis of mind.
- Computer science offers the computer as a model of human information-processing, computer programs as a medium to write cognitive theory, and artificial intelligence as a means of getting machines to perform "intelligent" operations.
- Social science, especially anthropology (and, increasingly, sociology) provides links between the cognitive processes of the individual human and the wider sociocultural world in which he or she moves.
For an historical
introduction to cognitive science, see The Mind's New
Science: A History of the Cognitive Revolution by Howard
Gardner (1985).The image at left, above, is Gardner's original
depiction of the cognitive hexagon. The image above and to the
right is an adaptation of the cognitive hexagon which serves as
the logo for UCB's Cognitive Science Students Association, which
includes majors in the undergraduate interdisciplinary Cognitive
Science program as well as students from other departments.
Psychology is certainly a
cognitive science, because it is concerned with the acquisition,
organization, and use of knowledge -- in short, with human intelligence.
As a cognitive science, psychology is concerned with a variety
- Sensation and Perception: how we process information about the external and internal environment; how this information reaches us, and how it is transformed into mental representations of the objects and events we encounter in the world.
- Attention: how we are able to turn our minds deliberately and selectively toward some objects and events (or their representations), and ignore others.
- Memory: the nature of knowledge stored in the mind, the processes of remembering and the causes of forgetting.
- Thinking: how we reason about our experiences, make decisions and choices, sort objects and events into other categories and make other judgments about them, and how we solve problems set by the environment and by our personal goals.
- Language: how we use words to represent objects and events, solve problems, and communicate our ideas and experiences to other people.
Historically, cognitive science emerged at a time when psychology, under the influence of radical behaviorism (see above), abjured mentalistic concepts. Cognitive science is interested in more than human mental functioning -- for example, some approaches to artificial intelligence take no interest in "how the mind does it". Still, so far as understanding human mental functioning is concerned, cognitive science does nothing that psychology is not capable of doing so as well, and had it not been for the aberration of behaviorism might never have been developed.
Psychology's status as a cognitive science stems, in part, from the historical preoccupation of philosophers with problems of knowledge. But psychology is not just a cognitive science, because there is more to the mind than cognition. Remember Kant's "three irreducible faculties, and Hilgard's "trilogy of mind"?
So psychology is also an affective science, concerned with emotion, as well as a conative science, concerned with motivation. This was what James was getting at when he defined psychology as the science of mental life in its entirety, and what Hilgard meant when he reminded us that emotion and motivation were also part of mental life.
Psychologists, cognitive scientists, and neuroscientists sometimes use the term "cognitive" to refer broadly to all mental states, including emotion and motivation. But strictly speaking, the term cognitive refers to mental states of knowledge and belief, associated with perception, memory, thought, and language.
In some sense, cognitive science is broader than psychology, because it includes fields like philosophy, linguistics, and anthropology, that approach behavior from other perspectives. But in another sense, psychology is broader than cognitive science, because it encompasses emotion and motivation as well as cognition.
Psychology and Neuroscience
Psychology is also a component of another interdisciplinary field of inquiry, neuroscience -- which also got its start, and its name, in the early 1960s. Before that there was just neurology, a term dating from the 17th century, neurophysiology (first appearing in English in 1859), and neuroanatomy (1900).
As a biological discipline, neuroscience was initially organized into three branches: molecular and cellular neuroscience, concerned with neurons and other elementary structures of the nervous system -- the whole legacy of what Elliot Valenstein (2005) has called "the war of the soups and the sparks"; then there was systems neuroscience, concerned with how the various pieces of the nervous system connect up and interact with each other; and behavioral neuroscience, concerned with everything else -- but in particular with motor activity, basic biological motives such as hunger and thirst, and the operation of sensory mechanisms -- mostly without reference to mental states as such.
But pretty quickly there began to emerge a fully integrative neuroscience (Gordon, 1990), concerned with making the connections between the micro and the macro, the laboratory and the clinic, and between neurobiology and psychology.
First to make its appearance was cognitive neuroscience, concerned with the neural bases of cognitive functions such as perception, attention, and memory. As with cognitive science, some practitioners of cognitive neuroscience defined "cognitive" broadly, so as to include emotional and motivational processes as well -- really, any internal state or process that intervened between stimulus and response. But, again strictly speaking, cognitive neuroscience is concerned only with the neural substrates of cognitive processes such as perception, attention, memory, thought, and language.
Psychology also contributes to a third interdisciplinary field, sensory science, which attempts to understand how the special senses -- vision, hearing, etc. -- work. This endeavor involves psychologists, physicists, biologists, biochemists, and engineers who devote themselves to the study of optics, acoustics, and the chemical senses (smell and taste).
By analogy with cognitive science and cognitive neuroscience, a new interdisciplinary field, affective science (or, sometimes, affective neuroscience; see below), has emerged to address questions about emotional life. The idea that there should be such an effort, separate from but parallel to cognitive science, implicitly reflects an acceptance of Kant's idea that cognition and emotion are irreducible faculties of the mind. Politically, it is also an attempt to break the hegemony of the cognitive in psychological analyses.
There isn't a conative neuroscience yet, interested in human motivation, though a lot of behavioral neuroscience is interested in eating, drinking, sexual, and parenting behavior in nonhuman animals).
But there is already a field of social neuroscience.
All this neuroscience testifies to our ability, at long last, to uncover the neural substrates of mind and behavior. At the same time, the emergence of behavioral, cognitive, sensory, affective, and social neurosciences underscores the value and status of psychology, which is interested in both cognition and emotion, as well as motivation, the individual and the social context. It seems unlikely that a complete understanding of either cognition or emotion can be obtained without some appreciation of the other. If so, cognitive and affective sciences will be necessarily incomplete approaches to the mind, and cognitive and affective scientists might just as well be psychologists instead.
However, just as not all
psychologists are interested in biology (biology is a tool for
psychology, but it is not an obligation, and many psychologists
do their work without ever thinking about how the brain
operates), not all neuroscientists are interested in the mind
(some are interested in purely biological questions about how
the brain and the rest of the nervous system works, variants
called molecular, cellular, and developmental
neuroscience, but which are hard to distinguish from
plain neurobiology). Even so, many neuroscientists use
techniques developed in the psychological laboratories to ask
purely biological questions about the nervous system.
Some psychologists are so
taken by the possibilities of modern neuroscience -- brain
imaging and all the rest -- that they have redefined themselves
as neuroscientists. That's fine, if that's what they want
to do, but sometimes they seem to forget that the neuroscience
that interests them depends utterly on psychology. That is
because they are interested in the neural basis of mental life,
and psychology is the science whose job it is to describe mental
life in the first place. If the psychological description
is wrong, the neuroscience will be wrong as well. As I
have put it (2010):
Psychology without neuroscience is still the
science of mental life; neuroscience without psychology is just
the science of neurons.
Applications of Psychology
Psychology has intellectual value because it contributes to our knowledge of ourselves and our place in the universe. But it also has social value, because it can be applied in the service of human adaptation: to help people to cope with the demands of their physical and social environments, and to actualize their potential as human beings. Using psychological knowledge to change ourselves, and our environments, we can better satisfy our needs, wishes, and hopes.
Thus, psychology is not just
an academic, intellectual exercise; it is concerned with
application as well.
- Education, with its emphasis on the acquisition and use of knowledge, especially in children, can be considered to be a combination of applied cognitive and applied developmental psychology.
- Artificial intelligence attempts to develop computers (or machines controlled by computers) that can perform functions usually attributed to human intelligence: robotics, picking up flaws in manufactured goods, reading X-rays, making medical diagnoses and other judgments, and language translation.
- Child rearing can also be considered a kind of applied developmental psychology, insofar as parental behavior can be changed for the better by a more sophisticated understanding of the processes of cognitive development, personality development, and socialization.
- Psychotherapy relies on basic scientific knowledge about normal mental functioning, which serves as a backdrop against which mental abnormalities can be understood; this knowledge, in turn, serves as a scientific basis for treatment and prevention.
- Psychological medicine (sometimes called behavioral medicine) seeks to use psychological knowledge to foster healthy behaviors and change unhealthy ones. There is a link between mind and body, and it is clear that beliefs, feelings, and motives can affect bodily functioning.
- Human resource management, an important component
of industrial and organizational psychology, applies
psychological principles to personnel selection and various
aspects of labor management.
Through application, scientific psychology can be used to promote and improve human relations (the relations between people), human engineering (the relations between people and the machines they use), and human ecology (the relations between people and their surrounding environment).
The Place of Psychology in Human Inquiry
Most students entering
college intend to take the introductory psychology course, even
if they have no intention of majoring in psychology, and for
good reason. In 1998, the American Association of Colleges
and Universities defined a liberal-arts education as one which
"fosters a well-grounded intellectual resilience, a disposition
toward life-long learning, and an acceptance of responsibility
for the ethical consequences of our ideas and actions". So
defined, "liberal arts" is independent of any discipline, and
covers everything from English Literature to civil engineering
-- if properly taught and studied. But certainly,
psychology -- understanding our minds and how they work, and why
we do the things we do -- is central a a liberal-arts education.
- Psychology shares with philosophy, theology,
literature, and art, an interest in the nature of
human existence and the sharing of individual experience.
- Psychology shares with economics, sociology, cultural
anthropology, and history an interest in the relation
of individuals to society.
- Psychology shares with biology and physical anthropology an interest in the relation of humans to other creatures.
- Psychology shares with physics, chemistry, and cosmology an interest in the place of humans in the universe as a whole.
Steven Weinberg, a Nobel laureate in physics, has written that "the effort to understand the universe is one of the very few things that lifts human life above the level of farce, and gives it some of the grace of tragedy". Whereas literature and the arts are concerned with individual experiences and expressions, psychology is interested in discovering generalizable laws governing human mental life and behavior. Whereas other natural and social sciences study the universe outside the individual, psychology studies what Morton Hunt (1993) has called "the universe within" the individual mind.
For an excellent, nontechnical, historical overview of psychology, see Hunt, M., The Story of Psychology (Doubleday, 1993). For a more technical history with emphasis on American contributions (essentially, a combined history and introductory text), see Hilgard, E.R., Psychology in America: A Historical Perspective (1987).
For short essays on a wide variety of psychological topics (great bedtime or bathtub reading), see Gregory, R. (Ed.), The Oxford Companion to the Mind (1987).
For a short history of Western philosophy, out of which scientific psychology grew, see Kenny, A., (Ed.), The Oxford History of Western Philosophy (Oxford University Press, 1994). For a more technical introduction to the modern philosophy of mind out of which scientific psychology emerged, see Flanagan, O., The Science of the Mind (2nd Ed.).
For an essay on developments in psychology from 1967 (when I took introductory psychology) to 2017 (when I taught my last intro course and retired from the University), see "50 Years of Psychology: A Personal Look Back a "Intro".
This page last revised 01/16/2021.