The Puzzling Leap from the Mind to the Body:

Psychosomatics

As interesting as the neural correlates of consciousness are, they represent only one side of the mind-body problem -- to wit, how does body affect (i.e., produce) mind? The other side is represented by the question of how the mind affects the body.

In philosophy, this is commonly discussed in terms of the problem of free will. We know (or we think we do) that our thoughts, feelings, and desires causes us to do what we do. But in psychology and psychiatry, this aspect of the mind-body problem is represented by the problem of psychosomatic interactions -- that is, physical diseases that are somehow caused by the patient's beliefs, attitudes, feelings, and other mental states.

In his Notes Upon a Case of Obsessional Neurosis (also known as the case of the "Rat Man", 1909/1953), for example, Sigmund Freud wrote of "the leap from a mental process to a somatic innervation, which can never be fully comprehensible to us". He repeated the point in his Introductory Lectures on Psycho-Analysis (1916-1917), referring to the "puzzling leap" from the mind to the body.

The leap from the mind to the body is at least as mysterious as the leap from the body to the mind. So, another project for science is to find out how the brain does this -- how, precisely, beliefs and other conscious mental states affect the functioning of our bodies, as reflected in phenomena like placebo effects and psychosomatic interactions.

But first we have to discover whether, indeed, we need to take such things seriously. There is a medical literature which disputes the importance, and even the existence, of psychosomatic effects.

Moreover, like dualism itself, psychosomatic effects have a bad reputation, being associated with a kind of vulgar form of Freudian psychoanalysis in which a cigar, for example, is never allowed just to be a cigar. Consider the following formulations taken from Psychosomatic Medicine, a classic psychoanalytic treatise by Franz Alexander (1950):

Anorexia nervosa is caused by feelings of envy and jealousy
Peptic ulcers are caused by the conflict of infantile dependency with ego pride and aspiration
Bronchial asthma is caused by excessive unresolved dependence on one's mother
Essential hypertension is caused by chronic inhibited aggressive impulses
Rheumatoid arthritis is caused by rebellion against restrictive parental influences

Here, for example, is Alexander's (1950) psychoanalytic formulation of the etiology of peptic ulcer.

Infantile dependency leads to feelings of inferiority.
Unacceptable feelings of inferiority lead to narcissistic protest, overcompensation for the perceived inferiority.
As part of the overcompensation, the person increases his level of effort, resulting in competitive aggression against others.
Aggression leads, in turn, to feelings of anxiety and guilt, which paradoxically feeds into the infantile dependency that started the whole vicious cycle to begin with.
All this stress thus leads to increased gastrointestinal activity, including hyper-secretion of gastric acids, resulting in peptic ulcer.

Needless to say, there is absolutely no evidence for these kinds of formulations -- or, for that matter, any other specific statement of classical Freudian psychoanalytic theory. But that doesn't mean that there aren't genuine psychosomatic connections between the person's mental states and the physical condition of his or her body.

The Stress-Disease Connection

Ulcers are perhaps the classic example of the psychosomatic connection between stress and disease. A modern psychosomatic formulation of ulcers would abandon the Freudian mumbo-jumbo, and simply talk about the effects of stress.

Exposure to stress activates the "flight or fight" response described by Cannon -- and also the "Tend and Befriend" response more recently described by Taylor.
The flight or fight response entails activation of the sympathetic branch of the autonomic nervous system, one of whose effects is to interrupt digestive processes.
Prolonged exposure to stress progressively depletes bodily resources, leading to the activation of the parasympathetic branch of the ANS in an effort to restore them -- for example, by secreting gastric acid in the process of digesting food.
The secretion of gastric acid eventually burns a hole in the stomach lining, which is what a gastric ulcer is. (Similarly, a hole in the lining of the small intestine, or duodenum, is called a duodenal ulcer).
Of course, autonomic activation has a number of effects on the body, not just secretion of gastric acid. Ulcers occur, as opposed to some other disease process, in individuals for whom the gastrointestinal system is constitutionally vulnerable -- the weakest link in the body's defenses.

The proverb that "a chain is only as strong as its weakest link" is very old, tracing back at least as far as the English philosophical psychologist Thomas Reid, who wrote in his Essays on the Intellectual Powers of Man (1786) that "In every chain of reasoning, the evidence of the last conclusion can be no greater than that of the weakest link of the chain, whatever may be the strength of the rest". It may have been popularized by V.I. Lenin, the 20th-century Marxist revolutionary, who somewhere argued that "the world-front of imperialism breaks at its weakest link" -- which he thought was czarist Russia (see Smith, 1955).

For ulcers, at least in theory, the weakest link lies somewhere in the stomach. And there may be other psychosomatic illnesses -- or, at least, illnesses that have a psychosomatic component -- where the weakest link lies elsewhere in the gastrointestinal system. Irritable bowel syndrome (spastic colon), comes to mind, implicating the large intestine. But the body contains many other systems, and the proper functioning of their components may well be compromised by stress.

Perhaps the best documented effect of stress on the body, of course, is hypertension, or high blood pressure. Theodore Roosevelt, Woodrow Wilson, and Franklin Delano Roosevelt all developed hypertension while in office, and Bill Clinton (who, admittedly, also had a famous love of cheeseburgers) had heart surgery after leaving office. Famously (and controversially), Friedman and Rosenhan estimated that what Friedman called "Type A" behavior -- basically, leading a high-stress lifestyle -- increased risk for coronary heart disease by almost 100%.

More anecdotal, perhaps, is the loss of hair color. An article in the New York Times noted that President Barack Obama's hair had grayed noticeably in just 44 days as president ("44 Days in the White House, and the Hair? Grayer Already" by Helene Cooper, 03/05/2009). Actually, as the article notes, his hair began to gray noticeably even before he became President, perhaps a reflection of the stress of the two-year long campaign for the Democratic nomination, and then the presidency itself (the two photographs, taken from the Times website, show the President in 2007, on the left, and in 2009, on the right). Other presidents, including Bill Clinton and George W. Bush, also grayed noticeably while in office (but not Ronald Reagan, who was quite upfront about dyeing his hair).

Not anecdotal at all, research by Elissa Eppel, a psychologist at UCSF, has documented that exposure to chronic stress can shorten the telomeres, "caps" on the ends of chromosomes that serve to protect them during replication. Telomere length, in turn, is a biological marker for aging, meaning that stress actually hastens the biological aging process. (Image from "The Science of Living Longer and Better" by Fran Smith, National Geographic, 01/2023.)

Stress can cause, or at least exacerbate disease, and so it would make sense that stress reduction can be an important part of the healing process. And, in fact, there is considerable evidence that stress-reduction treatments, including biofeedback and various forms of meditation, can improve physical health. But there are limits to what stress-reduction can do. For example, a group of researchers famously reported that group psychotherapy led to an increase in survival for a group of women who had been treated for breast cancer. However, subsequent studies failed to confirm this finding, and the general consensus now is that the original finding was adventitious. Stress is bad for the body, and stress-reduction can help, the effects of stress and stress-reduction are likely to be at the margins, and psychological treatments for physical disease are probably best thought of as adjuncts, or complements, to standard medicine -- not as viable alternatives.

Psycho(neuro)endocrinology

In fact, this modern psychosomatic formulation lies at the heart of the stress-disease connection studied by contemporary health psychologists. It appears that exposure to psychological stress, whether acute or chronic, increases a person's risk for a whole host of diseases, including mental illnesses such as depression, but also physical illness (Cohen et al., 2007).

We've known for a long time that the body's exposure to stress involves the secretion of adrenalin into the bloodstream, as part of the normal, reflexive "flight or fight" response. But one of the consequences of this is the subsequent release of another stress hormone, cortisol. Cortisol is normally a good thing, because it reduces inflammation of bodily tissues, but when it is released chronically, as in prolonged -- really prolonged -- exposure to stress, it can have deleterious effects on bodily functioning.

Here are just a few of the physical consequences of the prolonged release of cortisol:

Increased susceptibility to the common cold.
In pregnant women, increased risk of preterm labor and birth.
Increased risk of weight gain, because stress hormones increase our preference for fatty, starchy foods.
Slower healing of wounds, because cells become desensitized to cortisol, which paradoxically increases inflammation.
Poor sleep, which actually increases people's daytime stress levels, creating a vicious cycle.
Exposure to high levels of stress increases a person's risk for cardiovascular disease by as much as 50%.
And it also increases the risk that an HIV-positive individual will progress to full-blown AIDS, and AIDS-related complications.
There is even some evidence that exposure to high levels of stress increases risk for cancer, especially those cancers that are virally mediated.

According to Cohen et al. (2007), evidence from a host of "natural experiments" shows that stress levels are statistically associated with the onset, progression, recurrence, and complications of many different diseases. More critically, Cohen and his colleagues (e.g., Cohen, Int. J. Beh. Medicine, 2005) performed a series of "viral challenge" studies in which they deliberately infected subjects (who consented, of course) with the virus (a coronavirus, as luck would have it, but not the one involved in the COVID-19 pandemic of 2020). Across five separate prospective studies, they found that the virus was not sufficient to cause the common cold. A host of psychosocial factors, including chronic stress, were also significant risk factors, while social support and other aspects of positive affect seemed to strengthen resilience. Neither the virus nor stress is sufficient to cause a cold, but both may be necessary

Current psychobiological work on the stress-disease connection focuses on two neuroendocrine interactions between the nervous system and the endocrine system (Cohen et al., 2007): the hypothalamic-pituitary-adrenocortical axis (or HPA) and the sympathetic-adrenal-medullary axis (or SAM).

The hypothalamic-pituitary-adrenocortical axis begins with the hypothalamus, a subcortical structure, which releases a substance known as the corticotrophin-releasing factor, or CRF. CRF, in turn, stimulates the pituitary gland to release the adrenocorticotropic hormone, or ACTH. ACTH stimulates the adrenal glands to secrete cortisol, which has a wide variety of effects on anti-inflammatory processes, the metabolism of carbohydrates, fats, and proteins, and glucogenesis.

The sympathetic-adrenal-medullary axis begins with activation of the sympathetic nervous system, during which the adrenal medulla releases the hormones adrenalin and noradrenalin. These catecholamines have a variety of systemic effects on the cardiovascular and pulmonary, hepatic (kidneys), skeletal, and immune systems.

These effects have stimulated the development of whole new branches of psychology devoted to the study of psychoendocrine and psychoimmune interactions (because these interactions are obviously mediated by the nervous system, and nobody wants to leave the neuroscientists out, these are sometimes called psychoneuroendocrine and psychoneuroimmune interactions, respectively.)

Defining Stress

That's all on the somatic side of the modern psychosomatic formulation. What about the psychological side -- in particular, what do we mean by stress?

A psychological definition of stress is implied in Walter B. Cannon's (1915) description of the "flight or fight" response. For Cannon, and others who are biologically inclined, "stress" refers to any environmental stimulus that elicits the "flight or fight" response from an organism. But from a psychological point of view, the environment that matters is the perceived environment. Which means that "stress" needs to be defined subjectively, in terms of the individual's perception of the environment.

Shelley Taylor, a social psychologist at UCLA who specializes in health psychology and the stress-disease connection, noted that Cannon based his description of the "flight or fight" response exclusively on the behavior of male laboratory animals. Further, she noted that females tend to give quite a different pattern of responses, which she characterized as "tend and befriend". According to Taylor, the "choice" between "flight or fight" and "tend and befriend" is largely determined by levels of sex hormones such as testosterone and estrogen.

Actually, though, the specific term stress was initially imported from physics and introduced into the psychological lexicon by Hans Selye (1936, 1956), as any event that challenges the organism's current level of physiological or psychological adjustment. Selye further distinguished between the distress caused by affectively negative events and eustress caused by affectively positive events. His point being that getting married can be as stressful as getting divorced.

Cohen and his colleagues (1999) offered a purely psychological definition of stress as "the perception that environmental demands tax or exceed adaptive capacity". Note, in this definition, that stress is instigated by perception. Objectively, it doesn't matter whether demands tax capacity. All that matters is subjective perception.

Resistance to Psychosomatics

At a theoretical level, psychosomatic effects might dramatically illustrate the causal efficacy of consciousness. At a clinical level, these psychosomatic effects might even be put to practical use. At the same time, there is some tendency among many biologically oriented psychiatrists and clinical psychologists to dismiss psychosomatic effects as mere folklore of a past age, beneath scientific contempt.

From the standard biomedical perspective "real" diseases have known biological causes, and the "real" causes of mental illness are biological (genetic, neurochemical) in nature. Even the websites of such established organizations as the National Institute of Mental Health (NIMH) and the National Alliance for Mental Illness (NAMI) vigorously assert that such syndromes as anxiety and depression are "real diseases" because we now think that we know something about their biological underpinnings -- as if mental illness was not "real" unless it had a neurobiological cause!

The Case of Ulcers

A good example of the controversy over psychosomatic medicine concerns ulcers. Traditionally, peptic ulcers, whether gastric or duodenal, were commonly attributed to stress, and thus counted as "psychosomatic" in nature. Nevertheless, among many psychotherapists the underlying belief persists that mental states can have effects on bodily processes.

Doubting Stress

However, the discovery by Marshall and Warren (1984) that patients with ulcers were infected by a particular bacterium, Helicobacter pylori (H. pylori) led many physicians to reconstrue ulcers as an infectious disease, discounting any psychological causes. In their initial study, Marshall and Warren examined samples from the stomachs of a number of patients who had sought treatment for gastrointestinal distress (presumed ulcers). H. pylori was present in more than 80% of patients who actually had ulcers, but only about 50% of patients who received diagnoses of gastric inflammation (gastritis), excessive bile, or who proved to have no disease at all. Their conclusion was that ulcers had an infection origin, in H. pylori. For this discovery, Marshall and Warren received the Nobel Prize for Physiology and Medicine in 2005.

Marshall and Warren's discovery lent strong support to those in the medical community who sought to deny the psychosomatic assumption that stress and other mental states could be the cause of physical disease. In fact, Steven Hyman, then a prominent biological psychiatrist at Harvard Medical School (soon to become the Director of the National Institute of Mental Health, and subsequently Provost of Harvard University), went so far as to write an article on the discovery entitled "Another One Bites the Dust" (1994) -- meaning that ulcers represented another case where a putative psychological cause had been disproved in favor of something biochemical in nature.

Now, there's no doubt that many mental illnesses, including schizophrenia and some forms of depression, have biochemical causes. But that does not mean that psychological factors don't play a role in them, or that psychological factors aren't important causal agents in other forms of mental illness -- or, more to the point of the present discussion, that psychological factors don't play a role in causing physical illness.

Under the psychosomatic hypothesis, diseases such as ulcers classify as mental illnesses because their presumed cause is -- well, mental. But the fate of ulcers exemplified a trend in the medical community (and, for that matter, among some psychologists) to prefer somatogenic over psychogenic theories of mental illness. For example, Ralph Gerard, a prominent American physiologist, once declared that "There is for every twisted thought a twisted molecule". More recently, Thomas Insel ("Faulty Circuits", Scientific American, 2010), Director of the National Institute of Mental Health, predicted that neuroimaging would eventually redefine mental illnesses as neurological illnesses".

The biologization of mental illness involves a number of aspects:

Mental disorders are construed as neurological disorders.
Biological explanations of mental illness (in terms of genetic factors, brain disorders, etc.) are preferred over psychological explanations (in terms of trauma, a history of stress, or other environmental factors).
Biological treatments (such as drugs) are preferred over psychological treatments (such as various forms of psychotherapy).
Discounting the role of psychological or psychosocial factors in physical disease and its treatment.

Doubts About H. Pylori

The discovery of H. pylori had implications beyond our understanding of ulcers, because it severely undermined the psychosomatic hypothesis in general. In fact, the whole category of "psychosomatic" or "psychophysiological" disorders disappeared from the psychiatric lexicon (or, at least, from later editions of the Diagnostic and Statistical Manual for Mental Disorders), to be replaced by a category of "Psychological Factors Contributing to Medical Condition". Nevertheless, it turns out that there is good reason to doubt a purely infectious origin for peptic ulcers, and every reason to think that stress plays a causal role in ulcers after all.

Note, first, that even in the original study of Marshall and Warren, the "normal" patients, who proved to have no ulcers (or any other disease) also had relatively high levels of H. pylori infection. This is actually more true even than it appears from the Marshall and Warren study. Marshall and Warren conducted what is known as a retrospective study of ulcers, which began with a number of patients who reported gastrointestinal problems, and then looked in their stomachs for evidence of H. pylori. It turns out that such retrospective analyses can exaggerate the role of various causal factors. A better estimate of the true strength of a causal relationship is provided by a prospective study which begins with a random sample of the population.

Just such a study was reported by Nomura et al. (1994), who looked for evidence of H. pylori infection in a sample of the population, and then diagnosed the patients as to whether they had gastric ulcers, duodenal ulcers, or no ulcers. As in the Marshall and Warren study, the vast majority of patients with ulcers proved to be infected with H. pylori -- approximately 90%. But the control subjects also showed high levels of infection: roughly 80% of patients who were free of the disease were infected with H. pylori.

It may well be that virtually everyone with peptic ulcers is infected with h. pylori. The bug is found in over 70-90% of ulcer patients.
But not everyone infected with h. pylori suffers from peptic ulcers. Studies like that of Nomura et al. have found h. pylori in the gastrointestinal systems of almost 80% of ulcer-free control patients! Epidemiological studies have confirmed what was already suggested by Marshall and Warren's initial retrospective study - -that roughly half the world's population is infected with H. pylori. But they don't all have ulcers.

Bacterial infection may be necessary for peptic ulcers to form, but it is not sufficient. Even Marshall, the discoverer of H. pylori, now doubts that it is the cause of ulcers.

Confirming the Role of Stress

Hyman has a point: "stress" is a hard concept to measure precisely -- especially if you count "positive" stressors like marriage as well as "negative" stressors like divorce. If you know someone has ulcers, it's all too easy to look back at his premorbid history and find some stressors, to which you can attribute the ulcer. What's needed is empirical evidence that stress can cause ulcers.

Ideally, you'd take two groups of subjects, subject one group to high levels of stress, and then conduct biopsies to determine whether they developed ulcers. Of course, nobody is going to do such a study -- at least not on humans. But precisely that kind of study has been done, in an animal model, by Bruce Overmier and his colleagues at the University of Minnesota (1997)

But how to operationalize stress? As noted earlier, physiologists, and many psychologists, prefer to define stress as any event which challenges an organism's current level of adaptation. A different approach is based on research by a number of psychologists from the field of animal learning -- including Overmier, Martin E.P. Seligman, and Steven Maier, who were the pioneers in this area (and who were all graduate students together at the University of Pennsylvania; and Susan Mineka and myself, who were in the next generation of graduate students at Penn, and very much influenced by their work. Together, Overmier, Seligman, and Maier discovered learned helplessness, in which prior experience with uncontrollable shock retards avoidance learning. Mineka and Kihlstrom expanded this work to propose a new perspective on experimental neurosis, in which laboratory animals appeared to show "neurotic" behavior as a result of various learning experiences. Mineka and Kihlstrom proposed that experimental neurosis was induced by aversive events that had one or both of two qualities:

They were unpredictable. For example, in a classical conditioning situation, there was no conditioned stimulus available to signal the impending unconditioned stimulus.
They were uncontrollable. For example, in an instrumental (operant) conditioning situation, there was no conditioned response available that effectively leads to reinforcement.

The critical factor here is that there is not just a history of aversive events. What's critical is that the aversive events were unpredictable, uncontrollable, or both.

In their experimental paradigm, Overmier and Murison (Current Directions in Psychological Science 1997, Behavioral Brain Research 2000) and their colleagues employed lab-raised rats who are presumably free of H. pylori infection -- or if they are infected, random assignment of rats to the various experimental conditions insures that the groups do not differ in this respect.

They then exposed the rats to an aversive situation known as restraint in water (RIW) -- the rat is enclosed in a clear (waterproof) tube, and then immersed in water for a period of time. This procedure reliably produces gastric ulceration in rats -- but, interestingly, only in rats who are conscious at the time RIW is applied. If they're anesthetized, and not immersed, then ulceration does not occur. Note that RIW is, almost by definition, an aversive situation that is uncontrollable: there's nothing the rat can do to get out of the enclosure.
Prior to the RIW induction, Overmier and Murison give rats a stress pretreatment consisting of a number of unpredictable or uncontrollable foot-shocks, in various combinations.

A shock that is predictable and controllable is what is employed in a standard avoidance-learning paradigm. For example, a tone CS predicts a shock US, but the animal can escape or avoid the shock by pressing a bar.
A shock is predictable but not controllable if the tone predicts shock, but there is nothing the animal can do to escape or avoid the shock.
A shock is controllable but not predictable if the shock is not signaled by the prior tone, but the animal can escape the shock once it is delivered.
A shock is unpredictable and uncontrollable if there is no tone CS to signal onset of the shock, and there is nothing the animal can do to escape the shock once it's delivered.

Then the rats are exposed to RIW, and finally they measure the degree of gastric ulceration that results.

The basic finding of their research is that prior exposure to unpredictable and/or uncontrollable shock increases the effect of RIW on ulceration. In one study, pretreatment with shock that was both unpredictable (P-) and uncontrollable (C-) increased ulceration, over what was observed following RIW alone; but less ulceration occurred when the pretreatment was unpredictable (P-) but controllable (C+). In another study predictable (P+) but uncontrollable (C-) shock also increased ulceration, over RIW alone.

Apparently, controllability is more important than predictability -- when the shock is controllable, ulceration is decreased. Because controllability is more important than predictability, Overmier and Murison label this the helplessness pretreatment.

Other studies confirmed the causal role of stress in gastric ulceration. Overmier and Murison have studied an animal model (rats) of peptic ulcers that shows a clear role for psychological stress in triggering ulcers. Ulceration is increased when the helplessness pretreatment is administered in the same environmental context as the RIW treatment. And ulceration was also increased when the rats received "free" shocks during the rest period following the RIW treatment -- the more so when the uncontrollable shocks are also unpredictable.

So, it turns out that stress, in the form of the acute RIW treatment, especially when it is preceded by the (more chronic) helplessness pretreatment, causes ulcers after all.

Extrapolating from the Overmier and Murison research, and with due regard to the discovery of H. pylori by Marshall and Warren, we can offer a diathesis-stress model for the development of ulcers. In medicine, including psychiatry, such models postulate that an acute episode of some illness (whether cancer or the common cold, schizophrenia or depression) is caused by the interaction of two factors, diathesis and stress.

The diathesis factor does not cause the disease, but renders the person vulnerable to some specific disease process. The individual then makes whatever adjustment he can to the presence of this diathesis factor.
The stress factor challenges the individual's adjustment to the diathesis.
An acute episode of illness occurs if the combination of diathesis and stress crosses some threshold. Or, put another way, the probability of an acute episode increases as a function of the interaction of diathesis and stress.

Applying this model to ulcers:

The experience of stress leads to the excessive secretion of gastric acid into the stomach (this is a normal activity of the parasympathetic branch of the autonomic nervous system, and kicks in during stress in order to restore depleted blood sugar).
The gastric acid then erodes the stomach lining, to an extent sufficient to cause ulceration.
H. pylori may increase the organism's vulnerability to gastric acid.
But stress leads to the excessive secretion of gastric acid in the first place, making H. pylori infection less critical.
Antibiotic treatments (such as Rantidine) eliminate H. pylori, and reduce ulceration.
But behavioral interventions aimed at stress-reduction also reduce ulceration.
Obviously, the best treatment involves both pharmaceutical and behavioral treatments.

The important thing to note here is that both unpredictability and uncontrollability are intentional states. They are "about" something in the world -- specifically, whether certain events, especially negative or stressful events, are predicable or controllable. By virtue of their intentional content, unpredictability and uncontrollability are mental states. To the extent that mental states of unpredictability and uncontrollability play a role in the genesis of ulcers, ulcers retain their psychosomatic character, and illustrate the influence of the mind on the body.

Placebos

Placebo effects have been called the "jewel in the crown" of psychosomatic medicine, because they appear to show how patients' beliefs about the treatment they are getting influence the outcome of treatment. In the standard definition (Shapiro & Shapiro, 1997),

Placebo refers to "Any treatment... used for its ameliorative effect on a symptom or disease but... [which] is not specifically effective for the condition being treated."
Placebo Effect refers to "The nonspecific psychological or psychophysiological effect produced by a placebo."

In clinical trials, placebos are typically used as controls to reveal whether new pharmacological agents actually have any specific effects on medical outcomes. In order to be approved by the US Food and Drug Administration, new drugs must be shown to be safe and effective -- the latter usually by comparison of the active drug to an inert placebo.

Doubting Placebos

Medicine, and the healthcare professions generally, has always had a vexed relationship with the placebo. Was it Hippocrates, or was it Galen, who enjoined physicians to use new medicines while they still had the power to heal -- acknowledging that something other than the intrinsic properties of drugs was critical to their success? In any event, long before Pepper (Pepper, 1945) and Beecher (Beecher , 1955) drew professional attention to placebo effects, physicians appreciated the importance of belief and suggestion in curing disease (for comprehensive coverage of placebo effects and related topics, see Benedetti, 2007; Harrington, 1997; Harrrington, 2008; Price, Finniss, & Benedetti, 2008; Shapiro & Shapiro, 1997). It was not long ago that placebo pills, labeled as such, were listed in the Physicians Desk Reference. Norman Cousins (Cousins, 1976) famously advocated placebo effects in medicine, at roughly the same time that the randomized clinical trial -- still the gold standard for evidence-based treatment -- effectively consigned the placebo effect to the status of a nuisance variable which must be overcome, instead of a catalyst to be capitalized on. The New York Times Magazine announced on its cover (January 9, 2000) the "astonishing fact" that "placebos work". But only a year later, not content merely to show that effective treatments are better than placebo, Hrobjartsson and Gotzsche (Hrobjartsson & Gotzsche, 2001a, 2001b) concluded that placebos had virtually no practical effects on clinical outcome -- leading the Wall Street Journal, in a May 30, 2001 commentary, to criticize the "Dale Carnegie school of medical thought". Nevertheless, the New York Times recently reported (May27, 2008) that a Maryland-based company, Efficacy Brands, proposed to market a cherry-flavored placebo named Obecalp (read it backwards) over the counter to reduce the use of active medications for children with minor ills, hypochondriasis, and other forms of abnormal illness behavior.

Why are placebos so controversial? In part, I think, it is because they appear to challenge the biological basis of medical practice. Beginning with the microbe-hunting of Pasteur and Koch, through the pharmaceutical revolution, the development of laboratory diagnostics and imaging techniques, and pharmacogenomics, a major trend in the scientific revolution in medicine has been the development of diagnostic and therapeutic techniques that minimize human interaction between physician and patient. Elsewhere, I have cited the "tricorder" or "feinberger", the hand-scanner used on Star Trek to diagnose and treat illness, as the apparent ideal for scientific medicine, because it obviates the need to take account of any psychosocial dimension of illness, prevention, or treatment (Kihlstrom, 2003). Scientific medicine, in this exclusively biocentric view, is simply a matter of treating germs with pills.

But the behavioral and social sciences are sciences too, and the placebo and related effects underscore the psychosocial dimensions of illness, prevention, and treatment: of the effect of the patient's (and the physician's) beliefs, attitudes, and expectations on the effects of those pills; on the role of human judgment in assessing symptoms, reading test results, making diagnoses, and choosing treatments; on the intrapersonal and interpersonal determinants of compliance, the importance of physician-patient communication and social support on treatment outcomes; the relationship between social class (and social status) and health. You can make a pill to treat an illness -- that's a matter of understanding the biology, but then you've got to get the patient to take the pill) -- and that is a matter of psychology and social science. The fact that Hrobjartsson and Gotszche, searching the entire medical literature, were able to find only 114 studies that compared placebo to a no-treatment control is powerful testimony to the widespread lack of interest in the placebo effect as an effect -- an effect that can be added to the specific effects of prescription drugs or other biological treatments.

But first things first: What's this about placebos being powerless after all. How can placebos be powerless, if the pharmaceutical industry has to take account of them?

The standard clinical trial contains two arms. In one, the drug condition, patients receive a drug which, supposedly, contains some pharmaceutical substance that affects some disease process. In the other, the placebo condition, patients receive the same capsule, except that it contains an inert substance -- a sugar pill. The placebo can be pharmacological, physical, or psychological, so long as it is plausible and inert. All the drug manufacturer has to do is show that the patients in the drug condition have a better outcome than those who received the placebo. But that's not enough to show that there is a placebo effect. The placebo is a control condition needed to show whether there's a drug effect. In order to demonstrate an effect of placebo, there has to be a control for the placebo as well -- in effect, a group that gets no treatment at all.

Because drug companies don't have to have such a group, there are remarkably few studies in the medical literature that have a no-treatment control group. Nevertheless, between their original 2001 study and a 2004 follow-up, (Hrobjartsson and Gotszche were able to identify 156 studies.

For those studies that had dichotomous endpoints (e.g., the patient's blood pressure was within the normal range or it wasn't), the relative risk ratio of the placebo group to the control group -- that is, the percentage of patients in the placebo group who got better divided by the percentage of no-treatment control patients who got better -- was almost precisely 1.0 (0.95, to be exact). Meaning that there was no difference between the two groups.
For those studies that had continuous endpoints (e.g., the patient's actual systolic or diastolic blood pressure), the size of the placebo effect, measured in terms of the standardized mean difference between the two groups, was equivalent to roughly 1/4 of a standard deviation (0.24, to be exact). The placebo effect was significantly greater in studies where the outcome was measured by the patient's self report (M SMD = .30), than when the outcome was measured by an objective observer (M SMD = .10).

Now, the H&G study has been criticized on a number of grounds -- chiefly, their exclusion of laboratory (as opposed to clinical studies), and their overly broad definition of a "placebo" to include almost any pharmaceutically inert treatment, no matter how implausible. But still, the onus is now on placebo researcher to demonstrate that placebos really do have effects, and that they are powerful enough to be respected by health-science professions.

But beyond whatever advantage they can provide in the treatment of illness, placebos are of theoretical interest because of the light they can shed on the problems of mind and body. Usually, the mind-body problem is framed as unidirectional: how brain processes can produce conscious mental states. But placebos, and other psychosomatic effects, remind us that there is another mind-body problem: how mental states can affect bodily functioning. Documenting these effects, and understanding their underlying psychological and biological mechanisms, is the great challenge posed by placebos.

Placebos and Pain

One area where placebo effects have been clearly demonstrated is in the area of pain.

For example, it turns out that placebos have "pharmacological" properties (Evans, 1974).

Placebos are more effective in treating severe than mild illness.
Placebos show a dose-response curve similar to that of the active drug to which they are being compared (i.e., two placebos work better than one).
Placebos show a time-effect curve similar to that of the active drug to which they are being compared.
Placebo "packaging" is important:

Placebos delivered intravenously are more effective than placebos delivered through intramuscular injection, which are more effective than placebos delivered orally.
And for placebos delivered orally, big, dark-colored, bad-tasting placebos are better than small, brightly colored, good-tasting ones.

Placebos create additive effects (i.e., drug + placebo is better than drug alone).
Placebo effects are influenced by patient beliefs about whether they have received a placebo, and about the effectiveness of the drug they're supposed to be getting.
Placebo effects are influenced by physician practices: doctors who frequently resort to medications get bigger placebo effects than those who do not.

A recent study by Ariely's group showed that the "price" of a placebo influenced that magnitude of the placebo effect. In the experiment, subjects rated their pain in response to a shock stimulus after taking a pill described as a "regular price" or "low price" analgesic medication. Of course, both pills were placebos. Compared to control trials, the subjects reported more pain relief from the higher-priced placebo.

Many consumers, and some physicians and drug companies, suspect that generic drugs, which cost less, are also less effective than their brand-name or reference-drug equivalents. And the Food and Drug Administration actually found that to be the case for Budeprion XL 300 mg, the generic equivalent of the brand-name Wellbutrin XL 300 mg. From a psychobiological point of view, this is puzzling, because by definition generic drugs are biologically equivalent to their brand-name reference drugs. All that is missing is the label. Where generics differ in effectiveness from their brand-name reference drugs, there may well be some as-yet unappreciated problem in manufacture. But it may also be the case that generic equivalents lack the "placebo power" of their brand-name equivalents, which carry both the cachet of a famous drug manufacturer and an extra cost.

The role of belief in placebo effects is dramatically illustrated by an analysis by Evans (1974, 1985) of studies in which placebos were compared to a number of different pharmacological agents in the treatment of pain. Remarkably, Evans found that placebo efficiency -- the ratio of positive outcomes with placebo to positive outcomes with drug -- was constant, at about .55, across a wide variety of drugs. In other words, if patients believed they were taking morphine, patients who really got placebo got roughly half the pain relief as patients who really got morphine; but if patients believed they were taking aspirin, those who really got placebo got roughly half the relief as patients who really got aspirin. Although Evans did not perform the analysis, the implication of his research is that patients who believe they are getting morphine will get more pain relief than patients who believe that they are getting aspirin, even though all are getting placebo!

Placebos and Depression

Another area where placebo effects have been found to be substantial is in the area of depression.

In a provocative paper entitled 'Listening to Prozac and Hearing Placebo", Kirsch and Sapirstein (1998) reviewed 28 published clinical trials of antidepressant medications -- tricyclics and tetracyclics (e.g., Elavil and Norval), selective serotonin reuptake inhibitors (e.g., Prozac), other antidepressants, and other medications that were not generally considered to be antidepressants, but which were being tested "off label" for their antidepressant effects. Each of these studies included a medication arm and a placebo arm. But, in line with standard practice, none of them included a no-treatment control group. For this purpose, Kirsch and Sapirstein turned to the psychotherapy literature, where the standard design includes a group of patients who get psychotherapy and a group that gets no treatment at all (e.g., by being put on a waiting list). In each of these studies, depression before and after treatment was measured by standard self-report questionnaires such as the Hamilton Depression Scale.

Comparing the standardized effect size in the drug and placebo conditions, Kirsch and Sapirstein found, much as Evans had with pain medications, that placebos were roughly 75% as powerful as the drug to which they were compared!
Psychotherapy (mostly cognitive-behavioral therapy) was about as effective as the drugs, and much better than a no-treatment control.
Based on all this information, Kirsch and Sapirstein drew the following famous (or infamous) conclusions:

From the no-treatment control group, K&S estimated that about 25% of the drug effect was actually due to "natural history" -- the simple fact that depression tends to remit spontaneously, at least to some degree, over time.
About 25% of the drug effect was actually due to the active ingredient in the capsule.
About 50% of the drug effect was attributable to placebo!

From their point of view, then, placebos are powerful indeed.

Kirsch and his colleagues (2002) made a similar point in a second study, which reviewed all clinical trials of SSRIs for depression, regardless of whether they had been published (for this they used the Freedom of Information Act to access the FDA database). Again, the placebo was about 80% as effective as the drug to which it was compared -- regardless of whether that drug was Prozac, Paxil, Zoloft, Effexor, Serzone, or Celexa). Unfortunately, this study did not include a no-treatment control group, but Kirsch's point is that there's little question that placebos are powerful in the treatment of depression - -almost as powerful as our most powerful drugs.

Link to a segment of 60 Minutes, interviewing Prof. Irving Kirsch and others on placebo effects in the drug treatment of depression, broadcast on CBS 02/19/2012.

Placebos and Irritable Bowel Syndrome

Placebos have also been found useful in the treatment of irritable bowel syndrome (IBS), which is characterized by abdominal pain, cramping, bloating, constipation, and diarrhea. However, there are no signs of physical damage to the gastrointestinal system, such as inflammation (which would lead to a diagnosis of inflammatory bowel disease, or IBD) or bleeding polyps (which might lead to a diagnosis of colon cancer). For this reason, thee are no specific tests for IBS (as opposed to IBD), and in fact IBS is only properly diagnosed when IBD, colon cancer, and similar diseases have been ruled out (it's also what makes IBS a syndrome instead of a disease). The lack of diagnostic signs has led some psychiatrists to suggest that IBS is a somatoform illness -- that is, a mental illness whose symptoms involve physical complaints. This point is controversial, but the fact of the matter is that the standard of care for IBS involves primarily psychosocial treatments, such as stress and lifestyle management, as well as prescriptions for antidepressants. Although IBS patients may also be instructed to alter their diet (mostly by drinking lots of prune juice!), few if any interventions are actually directed toward the gastrointestinal system.

In a recent series of studies, Ted Kaptchuk and his colleagues at Harvard Medical School have found that placebos lead to significant symptom relief in IBS patients. The studies are a little unusual in that they employ placebo acupuncture rather than placebo pills. From my own perspective, I would have thought that pills would be the obvious vehicle for delivery of placebos to IBS patients, simply because pills are swallowed and pass through the gastrointestinal system. But Kaptchuk runs a program in complementary and alternative medicine at HMS, where there's a great deal of interest in acupuncture. And while some physicians suspect that acupuncture is just a placebo itself, or at least mostly placebo, there is also such a thing as placebo acupuncture -- that is, a procedure that looks like acupuncture but which lacks the ostensibly active ingredient.

One mode of placebo acupuncture is to insert the needles in the "wrong" places. Acupuncture is based on a theory in Chinese traditional medicine that qi, or life energy, flows along channels known as meridians. Each meridian contains a number of acupuncture points. So, by avoiding the meridians, at least in theory, acupuncture will lack its essential ingredient -- that is, it won't affect the flow of qi. One of the reasons that many researchers have concluded that acupuncture is (mostly) placebo is that it doesn't seem to matter whether the needles are inserted at the points designated by traditional Chinese medicine.
Of course, the meridian theory might be wrong (at least, there's no anatomical evidence for meridians), but that inserting needles into the skin has some specific effect on the body, such as interfering with the transmission of pain signals (this is a hypothesis derived from Melzak and Wall's "gate control" theory of pain). Accordingly, a better placebo is to "pretend" to insert needles that do not actually break the surface of the skin. This can be accomplished by a trick analogous to a theatrical knife, blade collapses into the handle when it encounters an obstruction (like the "victim's" skin). In placebo acupuncture needles, the needle itself is attached to a spring such that it collapses when it touches the skin. And with topical analgesic applied to reduce the "pain of insertion", a bandage applied to "keep the needle in place", the patient is none the wiser. And that's what Kaptchuk did in the studies to be described.

Kaptchuk et al. (2008) randomly assigned a large group of IBS patients to one of three conditions:(1) Limited Placebo, in which patients received sham acupuncture but extremely limited psychosocial contact (2) Augmented Placebo, in which the patients received a considerable amount of face-to-face social support from the practitioner; and (3) a waitlist control which received no acupuncture and no practitioner-patient interaction. After three weeks of "treatment", the augmented acupuncture group showed significant improvement on all measures, compared to the waitlist controls, with the limited acupuncture group falling in-between. Some of these patients continued to receive sham acupuncture for another 3 weeks, with essentially the same result.

The remaining patients were shifted "true" acupuncture: the comparison of true vs. sham acupuncture yielded no significant effects (Lembo et al., 2009), which is consistent with the idea that acupuncture itself is a placebo treatment.

To make things really interesting, Kaptchuk and his colleagues (2010) actually told the patients that they were giving them a placebo -- and it worked. Patients given "sugar" pills clearly labeled as placebos -- what is called an "open label" placebo -- got significant relief of pain and other symptoms, compared to a control group that got no pills at all. But why would subjects respond to something that they had been told was pharmacologically inert? It has to do with the context in which the placebos were taken. Kaptchuk told the patients that placebos worked by mobilizing "mind-body self-healing processes". So, the patients didn't believe that the placebo was just an ineffective treatment; instead, they probably believed that placebos actually work through a psychosomatic process. So, the belief affected the functioning of the gastrointestinal system.

But it's one thing to believe you're being given an active drug, and to have that belief affect your physiology; it's another thing to believe you're being given a placebo, and to have that belief affect your physiology. Maybe the patients didn't believe that they were being given placebo. After all, in the balanced placebo design, some subjects who are told they're getting placebo get the active agent instead. On the other hand, maybe it's the instructions that come with the placebo that are critical. After all, the physician doesn't just hand a patient a pill, saying "This is a placebo, take it". Instead, in this study (and others of a similar sort conducted by Kaptchuk and his associates) the placebo is surrounded by an actively therapeutic context. Patients are informed of advances in mind-body medicine; they're encouraged to believe that placebos mobilize mind-body interactions; and they're told that their placebo has been "designed especially" for them and their particular problem. What it means, exactly, to have a placebo "designed especially" for a particular person and a particular problem isn't clear. But I suppose that just goes to emphasize the importance of the psychosocial context. Social psychologists tell us that beliefs are stronger when they're acquired in a highly persuasive context, and placebos appear to be no exception.

Kaptchuk argues that placebo effects aren't simply a matter of "mind over matter" -- that placebos have real physiological consequences. Placebos given for pain, for example, release endogenous opioids, cannabinoids, and dopamine (a neurotransmitter important in the brain's "reward" system). The usual explanation for placebo effects involves some sort of conditioning procedure. If delivering an active analgesic (analogous to an unconditioned stimulus) triggers a physiological response that leads to pain reduction (an unconditioned response), then delivering a placebo analgesic might act as a conditioned stimulus for the release of endogenous opiates as a conditioned response. It's a good hypothesis, and probably largely correct. However, it is undercut by instances where placebos are effective even though the patient has had no prior experience with the active drug.

Hypnosis and Psychosomatic Outcomes

Setting aside the effects of placebos per se, an increasing body of literature suggests that verbal suggestion -- that is, the communication of a belief from one individual to another -- can have effects on objectively measured physiological outcomes.

A number of controlled experimental and clinical studies in the area of psychosomatic medicine have employed variants of the symptom-provocation method familiar in the diagnosis and treatment of allergies and asthma. In this technique, a patient is stimulated with a substance hypothesized to cause an allergic reaction; if the allergen actually induces an allergic reaction, the patient is then treated with another substance, hypothesized to prevent or reduce the reaction (this is known as symptom neutralization).

For a variety of reasons, mostly historical, a great deal of research on psychosomatic interactions has involved hypnotic suggestions. However, it turns out that suggestion, and the beliefs that suggestion engenders, is more important than hypnosis per se.

Icthyosis

Perhaps the granddaddy of all such studies is a clinical report by Mason (published in the British Medical Journal, 1952, 1955) of a 16 year-old boy with congenital icthyosiform erythrodermia of Broq. Commonly known as "fish skin disease", this syndrome is a hereditary disorder affecting the skin, which becomes discolored and blackened, horny, inelastic, fissured, and peppered with vascular protuberances. The disease was extremely unsightly, not to mention distressing to the patient. Conventional treatment, involving skin grafts from unaffected portions of the body, failed: the new areas acquired the erythrodermia as well. As a last resort, Mason hypnotized the patient, and suggested that the lesions would go away. But -- and this is a very big but -- Mason did it right. First, he suggested that the skin would clear on the patient's left arm. After 5 days, the left arm -- but the left arm alone -- began to clear, and was completely clear after 10 days. Then Mason gave similar suggestions targeting the right arm, and then the patient's legs, and trunk. The progressive remission of the skin lesions, highly correlated with the suggestions, was documented photographically, both after initial treatment and at a 4-year followup. (Mason also attempted hypnosis with other cases of icthyosis, with varying degrees of success.)

Mantoux Reaction

In another classic of the hypnosis literature involved the Mantoux reaction, a diagnostic skin test for tuberculosis (still in use). After a subcutaneous injection of purified protein derivative tuberculin, a physician will measure the size of the induration -- a raised, hardened, red blister created by the injection. A positive reaction is indicated by a induration of a particular size.

Black (1963) studied four Mantoux-positive patients, all of whom were known to be highly hypnotizable, giving them a suggestion that "You will no longer react to the injection as you did before... no redness, no swelling, no heat, no itching, no pain...". And, for each of the four patients, that's just what happened. Compared to pre-suggestion measurements, both the size of the swelling and the size of the erythema (the reddened portion) decreased. However, a skin biopsy showed that the underlying histology was unaffected by the suggestion. The suggestion targeted the superficial, visible Mantoux reaction, and that's all that changed. But still!

Allergies

Mason employed a similar approach in treating difficult cases of allergic reaction.

In treating a case of pollen allergy that had resisted treatment for 10 years, Mason & Black (Lancet, 1958) found that the reaction could be suppressed by hypnotic suggestion, such that the patient showed no hypersensitivity to injected antigens. In one of those things that medical researchers used to do (and still do sometimes today), Mason injected the patient's serum into his own bloodstream, resulting in the usual hypersensitive reaction. The experiment indicated that hypnosis could somehow inhibit the action of IgE immunoglobins.
In a followup, Black (British Medical Journal, 1963a, b, c) tested 12 subjects who were known to be susceptible to allergic reactions. Six of the seven hypnotizable subjects were able to inhibit their allergic responses, while four of the five subjects of low-to-moderate hypnotizability were unable to do so.
Perhaps buoyed by his success with Icthyosis and allergy, Mason used hypnosis to treat a "Mantoux-positive" patient who was allergic to a skin test for tuberculosis. A hypnotic suggestion successfully inhibited the allergic reaction (published in Acta Allergolica, 1960).

A clinical series published by Collison (Medical Journal of Australia, 1975) included a large number of allergic patients seen over a 10-year period. Collison classified his patients by the "depth" of hypnosis they achieved during treatment -- an individual-difference construct roughly analogous to hypnotizability. In response to the treatment of their asthma by hypnotic suggestion:

Fully 19 of 43 hypnotizable patients were cured, showing complete remission, while another 17 were improved, meaning that their respiratory function now fell within normal limits.
Only 6 of 47 mediums were cured, and only 21 improved.
None of 31 insusceptible patients were cured, though 2 improved.

In a classic study, two Japanese investigators, Ikemi and Nakagawa (1962) employed a variant on the symptom-provocation method to study the effects of suggestion on a form of contact dermatitis (similar to poison ivy or poison oak) induced by contact between a person's skin and the leaves of the lacquer and wax trees common in Japan and other parts of East Asia.

Based on a survey, 13 male high-school students known to be sensitive to the leaves were recruited for the study. After they were blindfolded, their arms were brushed by the lacquer-tree or wax-tree leaves (depending on their sensitivity), and were given the suggestion that the plant was actually harmless: 11 of the 13 subjects showed a reduced skin reaction to the poisonous leaves. In another condition, they were brushed by the chestnut-tree leaves, but told they were the leaves of the lacquer or wax tree (depending on their sensitivity): all 13 subjects showed signs of dermatitis.

In other experiments along these lines, the sensitive students were challenged with extracts of the poisonous leaves, diluted in water, or with ordinary saline solution. These experiments yielded results quite similar to those obtained with the leaves themselves.
In a control experiment, the leaves were applied to another group of students, who had never experienced an allergic reaction to the poisonous plants. These students showed little reaction to the poison, but also showed little response to the suggestion that nonpoisonous leaves were poisonous. So, the belief has to be coupled with some prior experience, suggesting a role for something like classical conditioning.

Sometimes, the suggestions were given while the subjects were hypnotized, but not on all instances. Accordingly, hypnosis had nothing to do with the outcome. The controlling factor was the subjects' beliefs about what they were touching -- beliefs influenced by the experimenters' suggestion, but beliefs nonetheless. Beliefs that had physiological consequences.

Link to the study by Ikemi and Nakagawa (1962).

Warts

Similarly, there is a large clinical literature on the effects of hypnotic suggestion on dermatological warts.

Asher (1956), reporting the results of 33 consecutive patients treated for multiple warts, reported that 11 of 17 hypnotizable patients were cured after 10 weeks; 4 of 8 moderately hypnotizable patients were also cured; but none of 8 insusceptible patients were cured. Although warts often show spontaneous remission, meaning that they go away on their own, the fact that remission after 10 weeks occurred more frequently in patients of moderate to high hypnotizability than in unhypnotizable patients, it seems clear that something else is going on.
Sinclair-Gieben & Chalmers (1959) treated 14 patients with bilateral warts, with hypnotic suggestions that targeted only one side of the body. On followup after 3 months, 9 hypnotizable patients did show remission of the warts, but only on the targeted side of the body; 5 insusceptible patients showed no changes on either side.
Ullman & Dudek (1960) treated 62 patients with warts: at a 4-week followup, 8 of 15 hypnotizable patients showed remission, but only 2 of 47 insusceptible patients.
Surman, Gottlieb, Hacket, & Silverberg (1973) gave lateralized suggestions to patients with bilateral warts. Like the earlier investigators, they noted some improvement in 9 of 17 patients given suggestions, but in none of 7 patients assigned to an untreated control group. In contrast to the Sinclair-Gieben & Chalmers study, however, the improvement was nonspecific, occurring on both the targeted and the non-targeted side of the body.
Johnson & Barber (1978) found that remission of warts occurred in 3 of 11 subjects given hypnotic suggestions, but in none of 11 subjects given the same suggestions without a hypnotic induction.

In an attempt to straighten all of this out, the late Nicholas Spanos and his colleagues, performed a number of experimental studies of the effect of both hypnotic and nonhypnotic suggestions on warts. The results of the experiments are all the more remarkable because Spanos was well known for his skepticism regarding hypnosis.

Although the Johnson and Barber study seemed to indicate that hypnosis was a crucial variable, Spanos reasoned that hypnotic suggestions might have worked better simply because, by virtue of the myths and urban legends surrounding hypnosis, the hypnotic suggestions were more believable. Accordingly, Spanos, Stenstrom, & Johnson (1988) employed three groups of subjects. One received typical hypnotic suggestions for wart control. A second group received treatment from a plausible "cold laser" machine, that was actually a placebo. A third group received no treatment at all. At 6-week followup, the subjects who had received the hypnotic suggestions showed the greatest remission of warts.

In a second study, Spanos et al. (1988) compared four groups: hypnotic suggestion, nonhypnotic suggestion, relaxation without suggestion, and no treatment. The hypnotic and nonhypnotic conditions produced comparable results, leading Spanos et al. to conclude that the imagery contained in the suggestions, rather than hypnosis itself, was the major factor. In both experiments, similar studies have shown that both hypnotic and nonhypnotic suggestions can lead to the remission of warts.

Burns

Although much research remains to be done, it is fairly clear that hypnotic suggestion can facilitate the treatment of burns.

A laboratory experiment by Chapman, Goodell, & Wolff (1959) induced skin burns on both of subjects' arms by means of an intense light source (known as the Hardy-Wolff-Goddell dolorimeter). They then gave suggestions for hypnotic analgesia directed to one arm but not the other. The suggestions were effective in reducing felt pain, but the analgesic arm also showed less inflammation secondary to the burn.
A later clinical study by Moore & Kaplan (1983) involved five patients with bilateral burns, who received unilateral suggestions for increased blood flow to the site of the injury. Four of the five patients showed accelerated healing on the side targeted by the suggestion.

Although Collison's allergy study suggests that the effects of hypnotic suggestion on bodily function are correlated with the subject's degree of hypnotizability, other research suggests that hypnosis may not be all that important.

"Spontaneous" Orgasm?

This is a term given to episodes of sexual climax, male or female, that occur in the absence of physical stimulation of the penis, vagina, or clitoris. Long considered a myth, or an urban legend, there is now some evidence that people can think or imagine a sexual encounter that results in an actual physiological orgasm.

The roots of this idea lie in research by Barry Komisaruk and his colleagues (2004), who studied orgasm produced by tactile self-stimulation in paraplegic women -- that is, women who have suffered a complete break in the spinal cord at the level of the 10th thoracic spinal nerve (T10) or above -- that is, disconnecting the brain from the sensory nerves that supply the pudendal, pelvic, and hypogastric regions of the body. While that's interesting, it's not particularly surprising: erection and ejaculation in men are spinal reflexes which are preserved in paraplegia, provided that the peripheral nerves themselves have not been damaged. There's no reason why the same shouldn't be true for women. What was really interesting is that the women involved reported that they could feel the orgasm -- which isn't supposed to happen, given that the break in the spinal cord. Based on fMRI evidence, Komisaruk has suggested that these sensations are mediated by the Vagus nerve (Cranial Nerve X), which has both afferent and efferent components, and is spared in paraplegia.

Here's where the story gets interesting, because Komisaruk and his colleagues also obtained evidence that women (these subjects had intact spinal cords) could achieve full-fledged orgasms simply by engaging in erotic thoughts and imagery, without benefit of self-stimulation. Again, partly, this isn't surprising. It is well known that men can achieve erection simply by viewing erotic images, or reading or listening to erotic narratives; similarly, women exposed to erotic materials also show increased blood flow to the vagina, which is the female cognate of male erection. What's new, and surprising (at least to these researchers), is that women (more than half of those tested) can have complete orgasms merely by thinking erotic thoughts. This claim does not rely on self-report, because the physiological signature of orgasm is clearly apparent: by increases in blood pressure, heart rate, and tolerance for pain; moreover, fMRI shows that the so-called "pleasure centers" in the brain are activated during orgasms brought on by imagination, and those brought on by tactile stimulation. Moreover, women who imagined tactile stimulation of their breasts and genitals showed activation in the corresponding areas of somatosensory cortex.

Of course, these orgasms aren't exactly spontaneous -- it's not like they come unbidden, out of nowhere. They're produced by thought, and memory, and imagination. As such, they're yet another, if rather dramatic, example of the effect of the mind on portions of the body that lie outside the nervous system.

Suggestion, Belief, and Symptom Provocation

The fact that hypnosis is (probably) irrelevant to the psychosomatic effects of hypnotic suggestion has motivated some investigators to focus on suggestion alone, without any of the excess baggage associated with hypnosis.

Asthma

Luparello and his associates (1968, 1970) studied the effects of suggestion (nonhypnotic) on airway reactivity in asthmatic patients. Asthma is produced by constriction of the airway, as measured by the Ga/TGV ratio. Low Ga/TGV ratios induce a bronchospasm, or asthmatic reaction, which can be corrected by inhaling a neutralizer.

In one study, Luparello and his associates (1968) administered a placebo allergen, which reduced Ga/TGV ratios toward bronchospasm levels, followed by a placebo neutralizer, which returned Ga/TGV toward baseline.

In a more thorough study, Luparello and his associates (1970) provided patients with actual broncho-dilators or -constrictors, accompanied by suggestions that the device contained either a dilator or constrictor. When the patients were given an actual dilator their airways dilated, as expected; but there was less dilation when they were told that the dilator was a constrictor. Similarly, when the patients were given an actual constrictor, their airways constricted, as expected; but there was less constriction when they were told that the constrictor was a dilator.

The Luparello studies support the earlier findings of Ikemi and Nakagawa, and show that patients' beliefs can influence their bodies' physical reaction to allergenic substances.

Challenge Studies

The experiments of Ikemi & Nakagawa and Luparello et al. fall into an interesting category of medical research called a challenge study, most famously used in the testing of new vaccines. If you've got an infectious disease, and a vaccine that you think will prevent it, one way to test the vaccine is to give it to a bunch of people (and a placebo to a control group), and then see how many people in the vaccine group actually come down with the disease. Sometimes the placebo arm is omitted, and the vaccine group is simply compared to a group of people who didn't get any treatment at all. But this kind of clinical trial takes time, and usually requires testing of very large numbers of subjects (imagine, for example, that you're trying to detect the effect of a vaccine on a disease which affects only about 1% of those who have been exposed to it).

A quicker way to test a vaccine is to give it to a smaller group of subjects and deliberately exposing them to the disease -- the exposure is the challenge (of course, there has to be a placebo or untreated control group as well). The challenge method is very efficient, but it is also highly controversial, because it appears to violate the Hippocratic Oath to "first, do no harm". Medical ethics generally prohibits deliberately exposing people to a disease. But, as I say, its been done -- mostly when the disease itself is relatively benign (inconvenient, like allergy, rather than deadly, like polio), or when a rescue treatment (like an inhaler) is readily available. Challenge trials were used most famously by Edward Jenner in his work on the development of a smallpox vaccine (Jenner coined the very word "vaccine" in 1796). They've also been used in the development of vaccines for typhoid, cholera, and malaria, among other diseases.

For more on challenge trials in the context of the search for a vaccine against Covid-19, see "Researchers Debate Infecting People on Purpose to Test Coronavirus Vaccines" by Denise Grady, New York Times 07/07/2020). See also a draft report from the World Health Organization on guidelines for conducting challenge trials. As far as Covid-19 goes, the WHO suggests testing only young people (aged 18-25), because they are at least risk for severe illness, and using only relatively low doses of coronavirus, to reduce the risk even further. Arthur Caplan, an expert on medical ethics, and Stanley Plotkin, an expert on vaccines, wrote an article in Vaccine ("Extraordinary Diseases Require Extraordinary Solutions", May 19, 2020) whose title summarizes the case in favor of challenge trials (though they don't think there should be a placebo group).

"Open" vs. "Hidden" Treatments

Recently a new paradigm for the study of psychosomatic interactions has been introduced by Benedetti and his colleagues (2003). Inspired by both the placebo paradigm and the symptom-provocation paradigm, they compare two conditions, in both of which the patients get a treatment for their condition which is known to be effective. Thus, no placebos of any kind are involved. Instead, patients in the "open" condition are told that they are getting the treatment, while patients in the "hidden" condition receive the same treatment, only unbeknownst to them.

In a study of diazepam treatment of postoperative anxiety, patients who were told that they were getting the drug reported less anxiety two hours later than those who were not told; and when the administration was interrupted, patients who were informed of this fact reported an increase in anxiety, whereas those who were ignorant did not.

In a study of morphine for postoperative pain, patients who were told that they were getting the drug reported less pain, compared to baseline, than those who were not; and when the administration was interrupted, subjects who were informed reported a greater increase in pain than those who were not.

In a study of subthalamic electrical stimulation for Parkinson's disease, patients showed greater changes in movement velocity when they were told the stimulation had begun, and when they were told it had been interrupted.

Viagra

Another provocative example of psychosomatic interaction is presented by Viagra (Sildenafil ciltrate), a popular pharmaceutical treatment for male erectile dysfunction (commonly known as impotence). Men who take Viagra are able to achieve and maintain erection of the penis when they were previously unable to do so. Viagra is generally considered to be a biological intervention for impotence, and in fact its pharmacological action is well known:

Sildenafil effectively inhibits a substance known as PDE5.
This, in turn, enhances the effects of nitrous oxide (NO) on release of another substance, cyclic GMP (cGMP).
This in turn induces muscle relaxation and vasodilation, which in turn produce
Tumescence and full erection of penis.

What is not so well known is that Viagra does not achieve its effects in the absence of what is euphemistically called "sexual stimulation" -- either -- that is, it isn't an aphrodisiac:

Tactile stimulation (such as stroking the shaft or tip of the penis), by which we might be talking about nothing more than a spinal reflex that might occur unconsciously purely at the level of the spinal cord, without any involvement by the brain; or
Visual stimulation (like pictures of naked people in sexually provocative poses), in which case we are talking about something much closer to an intentional, and thus conscious, mental state.

To the extent that the physiological effects of Viagra are mediated by visual stimulation, we have a "psychosomatic" effect not unlike the role that stress plays in ulcers. In both cases, physiology isn't enough. Apparently, you've got to have the "right" state of mind.

Still, further research may be needed on whether sexual arousal enhanced by Viagra can be produced with only visual (or, at least, non-tactile) "sexual stimulation".

If tactile stimulation is necessary, then the effect may be mediated as an unconscious spinal reflex, solely at the level of the spinal cord, and without any involvement of the cerebral cortex.
If visual stimulation in sufficient, without any tactile stimulation, then the effect is less likely to be mediated at the level of the spinal cord, and looks "mental" enough to qualify as a genuinely psychosomatic interaction.

Counterclockwise?

Among the many claims for psychosomatic interactions, perhaps the most provocative is the idea of Ellen Langer, a social psychologist at Harvard, that psychosocial interventions can slow, or even reverse, the aging process -- that "turning the clock back" psychologically can turn the clock back physically as well.

In a groundbreaking study, Langer and Rodin (1975) assigned a group of elderly nursing-home residents to take care of a potted plant, and also gave them a greater degree of choice in their daily schedules. A control group was given no choices; they were also given a potted plant, but told that the nursing-home staff would take care of it for them. On a follow-up 18 months later, twice as many residents in the experimental group were still alive, compared to the control group. This outcome suggested to Langer that, in fact, psychosocial factors -- like having choice and responsibility -- could, indeed, have palpable effects on bodily states.

In a later experiment, Langer and her colleagues (1990) took this idea to even farther extremes. In 1981, a group of eight elderly men, all in their 70s, was recruited to live for five days in lodgings that had been systematically modified to resemble a typical environment in 1959 -- right down to the music played over the "radio", the programs on the "TV", and the magazines on the coffee table. In the dining room and lounge, they discussed topics that were current in 1959 as if they were just happening -- and always in the present tense. And they wore clothes in the style of the late 1950s. For the entire time, the men were treated as if they were 20-something years younger, and they were instructed to really live as they had lived then -- not just to enact a role, but to inhabit it (like a Method actor). Langer et al. reported that, as a result, the men actually became "younger" on a variety of physical measures, compared to a control group who lived in the same space but without the special decorations and instructions. The experiment served as the basis for The Young Ones, a reality series initially broadcast by the BBC in 2010.

Eight men, five days, it's a low-power experiment, but it supported Langer's belief that one's mindset could have palpable effects on physical health. As discussed in later lectures on Attention and Automaticity, Langer was also the earliest social psychologist to draw attention to the automaticity of much social behavior -- she actually called it "mindlessness", and she now explores the benefits of the opposite mindset, which she calls mindfulness -- not exactly the mindfulness associated with certain forms of Eastern-style meditation, as discussed in the lectures on Meditation, but simply active sentience -- taking note of changes in yourself and the surrounding environment, avoiding familiar categories, and other habits of mind.

And she's also become a vigorous proponents of placebos in medicine. In one experiment, Crum and Langer (2007) worked with a group of hotel housekeepers. One group was (falsely) informed that their work, cleaning rooms and hallways, was actually vigorous physical exercise; a control group performed the same physical duties, but were given no information (or misinformation). They found that the maids in the experimental group actually lost weight, and showed improvements on other health measures as well. Their interpretation was that believing that they were engaging in physical exercise produced the effects of actual physical exercise. Of course, such studies have to be done carefully. It might be, for example, that the maids in the experimental group, once reminded about the benefits of exercise, actually increased their exercise levels -- for example, by walking up and down service stairways instead of taking the elevator.

It's one thing for a placebo to relieve the non-insubstantial psychological component of pain. It's another thing entirely for hypnotic suggestion to reduce dermatological warts. Langer's research -- including an ongoing study testing whether a "counterclockwise" manipulation can reverse advanced cases of cancer -- is best viewed as an attempt to push the boundaries of mind-body medicine to its utmost limits.

Two (Maybe Three) Kinds of Psychosomatic Effects

As noted earlier, the placebo is the "jewel in the crown" of psychosomatic medicine. Unfortunately, most placebo research is on pain, and because pain is so subjective, placebo effects on pain might well be counted as instances of mental-mental causation -- that is to say, where a belief (that one has taken a drug) causes another belief (that one is not in pain).

This is also the case with respect to antidepressant medication. The placebo effects documented by Kirsch and his colleagues count as instances of mental-mental causation, where a belief (that one has taken a drug) causes another belief (that one is not in pain).

However, an emerging body of research suggests that placebos and other psychological interventions can have effects on objective, physiological outcomes as well. As always, further research is required.

Medicine commonly distinguishes between disease, defined as pathological anatomy or physiology, and illness, or the subjective experience of disease. If placebos affect only illness, helping patients to feel better, that may be enough. But if placebos affect disease as well, helping patients actually get better, that is even better, especially for those who are interested in the mind-body problem (Kihlstrom, 2008).

These considerations suggest that there are two, maybe three, quite different kinds of psychosomatic effects, which have to be distinguished.

Effects on Mental State: These are exemplified by placebo effects on pain or depression, which are, after all, mental states. The vast majority of placebo literature only assesses mental states, through self-reports such as pain ratings and depression questionnaires. Here, the primary question for research is whether subjects really do feel better -- whether the placebo produces genuine relief from pain or depression (or whatever), or whether subjects just say they do (which, unless you're a radical behaviorist, is not the same thing at all). Even so, these effects of one mental state on another mental state don't really count as psychosomatic effects. They would more properly be considered psychopsychic effects.
Effects on Central Nervous System: As scientists, we assume at least a kind of (interactive dualistic) psychophysical parallelism, if not some version of (materialistic) identity theory, that every mental state is correlated with some physical state of the nervous system. So, subjective pain must have its correlates in the brain (or somewhere in the central nervous system), and so must depression, anxiety, and all the other subjective mental states that people take pills for. Therefore, if placebos and other psychosomatic effects produce genuine changes in the subject's mental state, then these should be accompanied by genuine changes in the nervous system as well. So, if we could identify the neural correlates of pain and depression, a genuine placebo effect on pain or depression would have effects on brain function as well as self-reports. Here we get closer to genuine psychosomatic effects.
Effects Outside the Nervous System: The nervous system interacts with all the other systems in the body:

Endocrine system, consisting of the pituitary, adrenal, and other glands, plus the ovaries and testes.
Integumentary system, consisting of the skin, hair, nails, etc.
Skeletal system, consisting of the bones and joints
Muscular system, consisting of the muscles and tendons.
Cardiovascular system, consisting of the heart and blood vessels.
Lymphatic system, consisting of the lymph nodes, thymus, spleen, and tonsils.
Respiratory system, consisting of the nose, pharynx and larynx, and lungs.
Digestive system, consisting of the mouth, stomach, intestines, and anal canal, as well as the teeth, tongue, liver, gallbladder, and pancreas.
Urinary system, consisting of the kidneys, urinary bladder, and urethra.
Reproductive system, consisting of the testes and ovaries, internal and external reproductive apparatus, and the mammary glands.
Immune system, consisting of "Toll-like receptors", "B cells", and "T cells".

It is not surprising -- at least, not to a psychologist -- that belief, expectation, and suggestion can have effects on the person's own mental state. And it's not surprising -- not to a dualist or a materialist, anyway -- that beliefs, expectations, and suggestions can have effects on the state of the person's central nervous system -- given that mental states are produced by the brain to begin with. The most provocative, perhaps the most convincing, and probably the most revolutionary evidence for psychosomatic interactions will be found in the body outside the central nervous system. such evidence would be incontrovertible evidence for psychosomatic effects.

That there are such effects is assumed by most proponents of behavioral (or psychological) medicine, who take an interest in the connection between stress and disease, leading to the development of whole new fields like psychoneuroendocrinology and psychoneuroimmunology, which search for the biological mechanisms by which the mind effects the body.

More work needs to be done, obviously, but taken together, studies of stress and disease, placebo effects, and the physiological effects of suggestion and other forms of social influence indicate that there is still plenty of life left in the psychosomatic hypothesis that mind can affect the body. In the 1950s, the Soviet psychologist Platonov published a book on psychosomatic medicine entitled The Word as a Physiological and Therapeutic Factor (1955). Given the importance of words in representing our thoughts, ideas, experiences, and beliefs, Platonov's work may yet prove prophetic. By showing how mental states can exert effects on bodily processes, this literature offers a new perspective on mind-body relations. Mind is not just a product of the body. Body is also a product of the mind.

Studies of the neural correlates of consciousness suggest that we can't get away from self-reports of phenomenal experience. And studies of placebos and psychosomatics suggest that mental states influence bodily processes. It appears that mind matters after all!

For an interesting and illustrated!) discussion of psychosomatic and placebo effects, with particular attention to "spiritual healing", see "Mind Over Matter" by Erik Vance, National Geographic, 12/2016). The basic question addressed in the article is: "How does a belief become so potent it can heal?".

Embodiment

In the psychosomatic syndromes, the patient's mental state affects objectively observable changes in anatomy and/or physiology outside the nervous system -- causing ulcers, acne, dysmenorhea, and the like. In some respects, the opposite side of the coin is represented by embodiment -- the idea that mental processes can be shaped by bodily states, the sensorimotor context in which they occur. The general idea behind embodiment is that cognition occurs in a widely distributed system that includes the body and the environment as well as the head.

Embodied cognition has been formally defined by Glenberg et al. (2013) as follows: thinking is grounded in action. This viewpoint is reminiscent of Bruner's famous adage, and here I am paraphrasing, that "The purpose of perception is action"). These actions are performed by bodies in environments. Thinking (by which Glenberg means al cognition) is not divorced from the body, but is strongly influenced by both the body and the environment.

Recall from the lectures on The Mind-Body Problem that UCB philosopher Alva Noe has expressed similar ideas about consciousness itself. While most philosophers would simply say that consciousness is a product of brain processes, Noe believes that brains are necessary, but not sufficient, for consciousness. Consciousness also requires a body, which is in communication with the brain, and an environment to be conscious of.

Goldinger (2016), a colleague of Glenberg's at Arizona State University (who is actually a critic of embodied cognition), has summarized embodiment in terms of six principles.

Cognition is influenced by the body. Cognition is constrained and biased by emotion and intended actions.
Cognition is situated in the environment (which gives situated cognition its name). Cognition is also constrained and biased by the immediate situational context.
Cognition can be "off-loaded" to the environment. A great deal of cognition takes place not in individual brains, but rather in the external world. A simple example is a grocery list: if we write down the things we want to buy at the store, we don't have to remember them. Recall that Plato, in the Phaedrus, objected to the proliferation of writing on the grounds that people who relied on it would suffer a weakened memory. Similarly, Daniel Wegner and his colleagues (1985, 2011) have argued that algorithmic search engines such as Google have become a kind of external or transactive memory where "information is stored collectively outside ourselves" instead of in our individual heads.
The cognitive system extends to the environment. Cognition is distributed between individual brains and the environmental context.
Cognition is for action. The Brunerian point of view again. At its simplest, this simply means that cognition evolved to support adaptive behavior.
Cognition may not involve symbolic representations. This is, perhaps, the most controversial claim, and one that splits the embodied cognition movement.

Many cognitive psychologists think that knowledge is represented in the mind amodally, as abstract symbols -- perhaps like the 0s and 1s in a computer, rather than as modality-specific images.

Actually, most cognitive psychologists acknowledge that there are both abstract "meaning-based" knowledge representations, and concrete "percption-based" ones, such as visual and auditory images.

The strong version of embodied cognition denies that there are any abstract, amodal knowledge representations at all. Instead knowledge is embodied in sensory experience and motor action. Our knowledge of the world consists in what Gibson would call its affordances for action.

The weak version of embodied cognition allows for abstract knowledge representations, but argues that embodied knowledge goes beyond mental imagery, and is a lot more important that cognitive psychologists think it is.

Embodied cognition is also sometimes called grounded cognition. Larry Barsalou, a leading figure in the embodied cognition movement, is among those theorists who actually denies that knowledge is represented symbolically. Instead, he argues that cognition is grounded in perception, action, and experience. He argues that simulation is important for all aspects of cognition, and that retrieving and using knowledge entails a re-enactment of the experiential states that accompanied knowledge acquisition. Among the examples he cites:

The importance of mental imagery and other forms of perception-based knowledge representations.
The cognitive linguistics promoted by UCB's George Lakoff, who argues that we reason in terms of metaphors that are "grounded" in knowledge of the body and the environment (e.g., "He's falling in love").
The neuroscientific discover of mirror neurons and mirror circuits in the brain, by virtue of which perception of an action activates not only visual centers but also motor centers that would perform the action being observed.

Similarly, in Mind in Motion (2019), Barbara Tversky (widow of Amos Tversky, in case you were wondering) has argued that our status as animals -- that is, animate beings -- who act by moving around in a physical world, lies at the core of our cognitive abilities. Like other proponents of embodiment, she challenges the notion that mind is an abstract entity independent of the body. Human minds can't be duplicated by silicon chips, much less beer cans linked together by string (as a famous argument for Strong AI imagined). She notices, for example, the number of "motion" metaphors for thinking: "arrange and rearrange, enlarge, stretch, join, copy, add, scramble, subtract, lift, glue, push, fold, mix, toss, embellish, separate, nail, scatter, bury, eliminate, turn, elevate, and poke holes in both real objects and mental ones". These metaphors for thought, all involving motion in and through space, give her hook its title. Like some other theorists of embodiment, she points out that, at least since the invention of writing, and even more so now in the age of the internet and Google, minds aren't the only things that perform cognitive work. Much of it is offloaded into the physical world.

Embodied Perception

The program for embodied cognition has been worked out most thoroughly in the domain of perception -- which is quite reasonable, considering that perception is so closely tied both to sensory experience and action (remember the Brunerian aphorism: "The purpose of perception is action").

To demonstrate what research on embodied perception looks like, consider a program of research on slant perception by Dennis Proffitt and his colleagues at the University of Virginia. Slant is one of the basic problems in perception, along with the perception of size, distance, motion, and figure-ground relations. For example, perception of slant is important if you're going to walk up a hill or climb a set of stairs. In his experiments, Proffitt asks subjects to estimate the slope of an actual hill located on the (very hilly) UVA campus.

By way of comparison:

The typical slope of a residential staircase is about 30º.
The Lombard Street Hill in San Francisco, famous as "the crookedest street in the world", and generally considered ( as the steepest street in the City (albeit wrongly: it's actually #10), has a slope of 31º -- which is reduced to a mere 16º if you look only at the slope of the street.
American highways rarely have grades larger than 6%, which corresponds to roughly a 3º angle (the steepest slope I can remember being labeled on I-5 is 9%, corresponding to 5º).

Anyway, Proffitt asked his subjects to make their estimates in three different ways.

Verbally, in terms of degrees.
Visually, by adjusting a modified protractor to match to the slope of the hill.
Haptically, by adjusting a palmboard (without actually looking at it).

When subjects make verbal estimates of slant, they overestimate wildly. Maybe it's because they have an inaccurate sense of angles, but that can't be the whole story, because their visual estimates, which don't require them to state an angle in degrees, are also inaccurate. But haptic estimates are very accurate indeed.

Subjects who are (relatively) fatigued from jogging also grossly overestimate the slope of a hill, as do subjects who are carrying a heavy backpack. But not if they make their estimates haptically instead of verbally or visually.

Proffitt's explanation is that the verbal and visual tasks reflect the subject's explicit, conscious perception, "in which hills look steeper than they are" -- a kind of visual illusion. By contrast, the haptic task is very accurate, because it is closely tied to the body's mechanisms for visually guided action, and not susceptible to the illusions that affect (infect?) conscious visual perception. conscious overestimation is actually adaptive. Consider the kinds of hills we encounter in everyday life, like 1º-9º. We can manage these, but the difference between, say a 5 slope and a 6 slope is actually quite significant for locomotion. In psychophysical terms, that's where overestimation tends to occur, and that's where overestimation tends to occur. If we overestimate the slope of a 6º grade, we'll be motivated to try to find an easier climbing route -- especially if we're tired or overweight. So overestimation is good for planning action. But this same overestimation is not good for actually executing action. Consider: even if we think that a 5º grade is actually 10º, when we go to climb it we don't actually lift our feet twice as high! No, because the perception that guides action is embodied, we lift our feet just the right amount -- no matter how tired or heavy we feel. Visually guided action, as opposed to visually informed planning, is closely linked to the body and the environment.

Embodied Emotion

Another area where embodiment plays an important theoretical role is emotion (e.g., Niedenthal, 2007). Mainstream cognitive psychology tends to think of emotion as an abstract "tag" added to the amodal, symbolic representation of some concept or experience -- "Weddings are happy occasions", "Dissections are disgusting", etc. (e.g., Bower, 1980). In contrast, theories of embodied emotion argue that emotions are grounded in, and represented by modality-specific sensory, motor, and interoceptive activity. In a manner reminiscent of the James-Lange theory of emotion, these patterns of physiological activation, when consciously perceived, are the emotion. And when emotions are remembered, or thought about, or perceived in other people, these same patterns of physiological activity are reinstated, so that the emotional state itself is re-experienced. More to the point, in the context of mind-body relations, when these emotion-specific bodily states are reinstated, the emotion itself is reinstated as well, and then spills over to affect cognitive processing -- shaping perception, memory, and thought.

Here are some examples from Niedenthal's work (disclosure: Paula worked as an undergraduate research assistant in my laboratory at the University of Wisconsin, where she was also strongly influenced by the perceptual-motor theory of emotion espoused by Howard Leventhal). Recall Paul Ekman's idea that certain basic emotions such as happiness, sadness, anger, and fear) are expressed as specific patterns of activity in the facial musculature. Niedenthal and others have discovered that forming these facial expressions, even in neutral stimulus situations, leads subjects to actually experience the corresponding emotions -- and for those emotional states to affect perception, memory, and judgment.

Subjects have markers (e.g., golf tees) affixed to the inside of their eyebrows. When the are instructed to bring the markers together, their faces take on a scowling expression -- and they actually feel anger and other negative affect.
If subjects are asked to hold a pen between their lips, they will feel sadness or other negative affect.
If subjects are asked to hold the pen between their teeth, they will feel happiness or other positive affect.

So, in these ways certain bodily states generate particular mental -- in this case, emotional states, even in the absence of relevant stimuli. Again, this happens because emotions are not represented abstractly and symbolically. Rather, emotions are embodied. Niedenthal writes (2007, p. 1003):

In theories of embodied cognition, using knowledge -- as in recalling memories, drawing inferences, and making plans -- is thus called "embodied" because an admittedly incomplete but cognitively useful reexperience is produced in the originally implicated sensory-motor systems, as if the individual were there in the very situation, the very emotional state, or with the very object of thought. The embodiment of anger might involve tension in muscles used to strike, the enervation of certain facial muscles to form a scowl, and even the rise in diastolic blood pressure and in peripheral resistance, for example. The concept of reenactment and related concepts such as simulation, resonance, and emulation are widely accepted in theories of embodied cognition, but many different mechanistic neural accounts of it have been proposed. One promising possibility is that simulation is supported by specialized "mirror neurons" or even an entire "mirror neuron system," which maps the correspondences between the observed and performed actions.

Critiques of Embodiment

Theories of embodiment are all the rage now in some quarters, but they aren't without their critics.

For example, Mahon (2015; Mahon & Caramazza, 2008) has argued conceptual processing -- even thinking about concrete concepts, such as hammer and running is unimpaired in neurological patients with sensory-motor deficits. If so, then retrieving and using conceptual knowledge doesn't require any kind of embodied re-enactment. All that is required is abstract, amodal, symbolic representations of conceptual knowledge concerning characteristic features, subordinate-superordinate relationships, and the like. And, for that matter, there are other neurological patients with category-specific deficits in conceptual processing -- in classifying objects as animals, for example -- who have no sensory-motor impairments (Mahon & Caramazza, 2009). Therefore, the brain ystems for conceptual processing and for sensory-motor processing must be distinct. Or, put another way, conceptual processing is disembodied after all.

More generally, Stephen Goldinger et al. (2016) -- Goldinger is actually a colleague of Glenberg's at ASU! -- has proposed that, however much the notion of embodiment might inform our understanding of perception and emotion, it is simply irrelevant to a wide variety of topics in cognitive psychology, from attention (the cocktail party phenomenon and Stroop interference) through memory (the serial-position effect and the post-event misinformation effect) to language (the word-superiority effect and phoneme restoration effect) to thinking (insight problem-solving and the availability heuristic).

Goldinger et al. conclude that "The emperor has a body, but no clothes" -- but this seems unfair. There is clearly a case to be made for embodiment in aspects of perception that are closely linked to action, and also for emotion. But the strong view of embodied cognition, in which cognition is driven entirely by sensory, motor, and affective processes, is clearly wrong. There are two many counterexamples. But a weaker view is certainly viable:

knowledge can be represented both amodally (symbolically) and by modality-specific sensory-motor activities (such as mental images);
amodal and modality-specific representations are dynamically linked, so that they can influence each other; and
cognitive processing may result in the activation of sensory and motor processes.

This page was last updated 07/07/2020.