VARIABILITY OF REFIXATIONS IN INFANTS

In adults, visual fixation is a foveal function in which a single retinal locus of regard (the fovea) is directed to a point of regard in the stimulus. Because of the immaturity of the infant fovea, the question arises as to whether or not infants use a consistent retinal locus of regard to direct fixations. Consistency of refixations of a small eccentric target was quantitatively examined in infants and adults using a television-based corneal reflection eye tracker. The scatter of refixations for most infants extended beyond the boundaries of the 1.5° square target but was not as large as the degree of central retinal immaturity that has been reported for infants. The mean standard deviation of scatter was about 0.8° [n = 73]. No trend in age (19-388 days) was found. This scatter was greater for infants than for adults instructed to fixate carefully (0.1°). However, uninstructed adults exhibited extensive scatter (0.4°, n = 25), and some showed more scatter than some infants. These results suggest that attentional factors limit the scatter in refixations more than sensory or oculomotor immaturity in the visual system. The implications of these findings for the measurement and calibration of infant looking behavior are discussed. © 1990.