Motion perception over long interstimulus intervals.

Recent studies using moving arrays of textured micropatterns have suggested that motion perception can be supported by two mechanisms, one quasilinear and sensitive to the motion of luminance-defined local texture, the other nonlinear and coding motion of contrast-defined envelopes of texture (Baker & Hess, 1998; Boulton & Baker, 1993b). Here we used similar patterns to study motion perception under conditions previously shown to isolate the nonlinear mechanism (low micropattern densities and positive interstimulus intervals [ISIs]. We measured direction discrimination for two-flash apparent motion over a much larger range of ISIs, and susceptibility to masking by incoherently moving "distractor" micropatterns. The results suggest that two nonlinear mechanisms can support motion perception under these conditions. One operates only for relatively short ISIs (less than c. 100 msec), is sensitive to small spatial displacements, and is relatively insensitive to distractor masking. The other operates over much longer ISIs, is insensitive to small spatial displacements, and is highly disrupted by distractor masking. These results are in line with previous studies suggesting that three mechanisms support motion perception.     

Operant GSR conditioning with cool air reinforcement

Two groups of 20 Ss each were run individually in a soundproof chamber heated to 115 F and humidified to 100%. Ss in the experimental group received brief presentation of cool air contingent upon emitted GSRs during 20 min of acquisition. Control Ss were matched one at a time in operant rate and were yoked one at a time to receive the cool air on a response-independent schedule. Both groups increased significantly in rate of unelicited GSRs during acquisition, with the experimental Ss’ curve rising more rapidly and both groups attaining equivalent terminal levels. During extinction, the groups maintained high levels of responding and did not differ. Examination of basal skin conductance data ruled out an activation hypothesis. In the control Ss, terminal response frequency was significantly correlated with percentage of fortuitous response-contingent reinforcement. It was concluded that both groups were conditioned, with the controls receiving intermittent reinforcement sufficiently often to elevate their responding. The cool air was judged to be an effective reinforcer of unelicited GSRs, perhaps more effective than those used in previous studies.     

Eyelid conditioning and concomitant GSR activity

The purpose of these experiments was to investigate an aspect of autonomic activity (namely, skin resistance) during the course of eyelid conditioning, as a check on those theories which postulate that ‘arousal’ or ‘emotionality’, as measured by autonomic activity, is related to the level of conditioning.

Although many measures of skin resistance were obtained (including both basal levels and responses), the results were with one exception entirely negative in showing no significant correlations between the autonomic variables and eyelid conditioning. The exception was a significant correlation between skin resistance change to a test-trial puff of air (the UCS) and the level of eyelid conditioning reached by the subject; this result supports predictions made by Spence about the role of a hypothetical emotional response in conditioning, but was obtained in only one of the two studies.

The generally non-significant relationship between skin resistance and eyelid conditioning is discussed with respect to response specificity, and also to a postulated specificity in conditioning such that a subject who conditions well in one modality does not necessarily condition well in another modality. This specificity is considered in the light of the physiological mechanisms involved in each response system.     

Motion perception over long interstimulus intervais

Recent studies using moving arrays of textured micropatterns have suggested that motion percep-tion can be supported by two mechanisms, one quasilinear and sensitive to the motion of luminance-defined local texture, the other nonlinear and coding motion of contrast-defined envelopes of texture (Baker & Hess, 1998; Boulton & Baker, 1993b). Here we used similar patterns to study motion percep-tion under conditions previously shown to isolate the nonlinear mechanism (low micropattern densi-ties and positive interstimulus intervals [ISIs]). We measured direction discrimination for two-flash ap-parent motion over a much larger range of ISIs, and susceptibility to masking by incoherently moving “distractor” micropatterns. The results suggest that two nonlinear mechanisms can support motion perception under these conditions. One operates only for relatively short ISIs (less than c. 100 msec), is sensitive to small spatial displacements, and is relatively insensitive to distractor masking. The other operates over much longer ISIs, is insensitive to small spatial displacements, and is highly disrupted by distractor masking. These results are in line with previous studies suggesting that three mechanisms support motion perception.     

Effects of operant conditioning on the GSR

Each of nine Ss was run for 11 daily sessions. Except for the first (operant level) and last two (extinction) sessions, 500-ohm drops in skin resistance were followed by reinforcement (light). These reinforcement periods lasted 20 min and were preceded by 10-min control periods during which no reinforcement was administered. Although the results showed no evidence for operant conditioning of the GSR, they did indicate that increased emission of GSR's occurred during the reinforcement period. This effect was shown to hold for Ss with low operant levels of GSR's but not for Ss with high operant levels.