The influence of flicker on infants' orienting toward peripheral targets

Purpose. Previously we showed that, for 3-month-olds, flicker enhances orienting in the temporal, but not the nasal, visual field (ARVO, 1996) Here, we report the results for 4- and 6-month-olds tested with the same procedure. Method. We used static perimetry to measure orienting toward 6° lights with a time-averaged luminance of 5 cd/m² that were either static or flickering at 6 Hz. We compared the proportion of eye movements toward lights located at 15° intervals along the horizontal meridian to the proportion in the same direction on control trials with no peripheral stimulus. Results. In two experiments with 4-month-olds (n = 120), flicker did not enhance orienting toward targets in either the temporal or nasal fields (ps > 05). For 6-month-olds (n = 60), flicker enhanced orienting toward all lights in the temporal field (p < .05), but not toward any light in the nasal field (p > .05). Inspection of the data for the temporal field shows that sensitivity to the static target increased most between 3 and 4 months while sensitivity to the flickering target increased most between 4 and 6 months. Conclusions. The results suggest different rates of maturation for pathways controlling eye movements toward static versus flickering stimuli in the temporal field The beneficial effect of flicker in the temporal but not the nasal field suggests that, as in adults (Posner & Cohen, 1980), subcortical pathways contribute to the control of infants' eye movements.