Effects on eye movements of requiring an immediate reporting response during human vigilance

12 subjects performed a vigilance task in which signals were presented in two squares of a display according to two variable-time schedules. The subjects reported any detections of the signals by pressing a key. Latencies of the reported responses should be less than 0.3 sec. or 1.2 sec. to be reinforced. Half of the subjects were informed of the signal frequencies while the other half were not. The former subjects showed longer durations of fixation for the squares providing more signals. Such differentiations were larger under the 0.3-sec, condition than the 1.2-sec. condition. The latter group of subjects showed neither of these effects. The results suggested that different degrees of immediacy of responding might engender different patterns of eye movements.