Development of saccade target selection in infants.

To investigate the development of the target selection process for saccade generation, saccade latencies toward one of two targets were compared with those toward a target presented alone, under conditions where the timing of fixation stimulus offset was varied. 12 2-mo.-olds (7 boys and 5 girls), 12 3-mo.-olds (6 boys and 6 girls), and 12 5-mo.-olds (8 boys and 4 girls) participated. The latencies were longer when two saccade targets were presented on the left and right sides of the display (Double-target condition) than when one target was presented either on the left or right side of the display (Single-target condition). The difference between the Single and Double-target conditions tended to be larger in 2-mo. old infants than in 5-mo.-old infants when a central fixation target remained on after the onset of peripheral stimuli (Overlap condition). However, there was no difference between the 2-mo.-olds and the 5-mo.-olds when the fixation target was turned off before the peripheral stimuli were presented (Gap condition). The results provided evidence of the maturational development of a target selection process for saccade generation during 2 to 5 mo. of age.