Humans perceive visual stimuli moving along the cardinal axes (up/down, left/right) better than stimuli moving along oblique (diagonal) directions, a phenomenon known as the oblique effect. We measured the directional tuning of adaptation to moving visual stimuli and found a corresponding oblique effect: the tuning width of adaptation was smaller for cardinal adapting stimuli relative to oblique adapters. We constructed a computational model of encoding of motion stimuli by cortical areas V1 and MT and decoding of stimulus information from the cells in MT (Rokem and Silver, 2009). This model accounts for a number of properties of directional anisotropies in motion perception and suggests that oblique effects could arise from anisotropies in stimulus encoding in the visual system combined with a decoding mechanism that employs a statistically optimal strategy to read out this information.