In a discrete-trials, two-key choice situation, probability-learning by pigeons was studied under a variety of training conditions. Matching was found in simultaneous and in successive problems, but a spatial problem produced only maximizing. In the simultaneous problem, noncorrection produced maximizing, while correction produced matching. Guidance produced maximizing when the animals were required to earn each opportunity for choice by pecking a center key on FR-5, but matching when the center key was not used. In a discrete-trials one-key situation, with latency as the measure, frequency and probability of reinforcement were varied independently. Differences in probability produced differences in latency of response, but differences in frequency did not.

Since a change of stimulus is required to effect a visual response, and since saccadic eye movements change the locus of the retinal image, the hypothesis was developed that there should be a brain response following saccadic eye movement.- The hypothesis was tested experimentally by averaging the activities following successive saccadic eye movements. A response was found whose characteristics were dependent on illuminance of the stimulus.

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After preliminary threshold determination, each of 25 Ss was given 120 trials (24 blank, 96 signal) in a visual signal detection task, with signal presentation being recorded with S's EKG. There was no relationship between hit rate and phase of cardiac cycle whether assessed over four measured phases, or as the difference in hit rate for signals presented either in the P‐wave or the QRS complex. Implications for theory are discussed.

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