Adaptation to Visual Rearrangement: Role of Sensory Discordance

The relative contributions of proprioceptive and efferent information in eliciting adaptation to visual rearrangement were studied under two conditions of visual stimulation. Subjects permitted sight of their forearm under normal room illumination showed significant adaptation when the forearm was (a) moved up and down under the action of tonic vibration reflexes, (b) voluntarily moved through the same trajectory at the same pace, (c) viewed while still, and (d) viewed while the margins of the elbow were vibrated. The reflex movement condition elicited significantly greater adaptation than the other conditions. Subjects allowed only sight of a point source of light attached to their hand showed significant adaptation when the forearm was (a) reflexly moved, (b) voluntarily moved through the same trajectory at the same rate, (c) passively moved, (d) still, and (e) vibrated while still. Less adaptation occurred as the amount of proprioceptive information about limb position was decreased. The adaptation elicited by voluntary movements of the forearm and by reflex movements did not differ significantly. It is concluded that corollary-discharge signals may not be crucial in adaptation to visual rearrangement; a more important factor appears to be discordance between proprioceptive and visual information.

Perceptual Conflict and Alcoholics

30 unselected Ss, outpatients in a clinic for alcoholics, served in a visual-recognition experiment. Positive and negative photographs of common non-motivating objects were shown under time-controlled conditions of exposure. Alcoholics as normals showed that negatives are more difficult to recognize (required a longer exposure to produce recognition) than positives and that this difference increases as a function of difficulty or object complexity. The data also suggest, however, that alcoholics are absolutely and relatively less able to process conflicting visual information than normals. The latter finding led to the hypothesis that alcohol may serve to relieve sensory discordance for the alcoholic.