Significance of attentive fixation for the selection of saccade targets in different parts of the visual field of the rhesus monkey.

Two monkeys were presented with a task in which they were free to make a saccade to one of two simultaneously presented targets. The data from both animals show that the preference for one of the targets depends on at least two factors: (i) active and attentive fixation of the central fixation point at the time when the two targets occur; (ii) relative position of the two targets in the visual field. The results were different for the two monkeys with respect to the role of stimulus position in the visual field. However, both animals changed their preference systematically when the fixation point was turned off before the two targets occurred as compared to the case in which the fixation point remained visible. With respect to the paradigm (fixation point off versus fixation point on) the stimulus selection of either animal was constant throughout the several weeks of testing.