Human visual evoked response was investigated as a function of stimulus size of diffuse light (Experiment I) and density of patterned light (Experiment 2). The effect of rotation of the patterned light was also investigated (Experiment 2). The results obtained in Experiment 1 indicated that, the mean amplitudes of the evoked response components (Amplitude A, B, and D) significantly increased and the mean latencies of the evoked response components tended to decrease as the stimulus size increased. The results obtained in Experiment 2 indicated that no significant change was observed with the increase of the density and no clear effect of rotation was found.

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The present experiment was designed to investigate the factors affecting the resolution of the contingent negative variation (CNV). In the first session, 11 subjects were tested in a standard CNV paradigm. These subjects were then tested in a probability learning paradigm in which a red or green feedback light informed the subjects whether their choice of response was correct or incorrect. The feedback stimuli were presented .75, I, and 1.5 sec after the imperative stimulus. The results showed that the resolution of CNV occurred immediately after the motor response in the standard CNV paradigm. In the feedback paradigm, on the other hand, the resolution of CNV occurred only after the feedback stimulus. The results suggested that the resolution of CNV is contingent upon the psychological state of completion initiated by the feedback stimulus rather than the motor response.

The present experiment was designed to test the effects of interstimulus intervals between the response stimuli upon reaction time (RT) under the conditions of two fixed (10 sec and 20 sec) and two variable (5, 7.5, 10, 12.5, and 15 sec; 10, 15, 20, 25, and 30 sec) intervals of eliminating the physical preparatory stimulus, and to monitor heart rate (HR) for analyzing the relationship between RT and HR. The results obtained showed that the 10 sec fixed interval condition was associated with a fastest RT, being interpreted as an optimal interval in this experiment. For each of the variable conditions the longer intervals tended to show faster RTs. Some positive correlation between RT and HR was obtained during the latter part of trials. This might be interpreted by Lacey's hypothesis. 'Die problem of optimal interval in RT was discussed in relation to the theory of classical conditioning.

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