T-18. Vector summation in young infants

Immaturities in cortical visual processing make the retinocollicular pathway dominant in young infants' saccadic control. The superior colliculus appears to transform retinal position into saccadic commands by the summation or averaging of movement vectors associated with deep layer neurons. We explored the extent to which infants 2, 4, and 6 months of age would make saccades equivalent to the sum of individual retinal vectors of two simultaneous visual targets. Consistent with predic-tions that increasing cortical influence over saccade generation would diminish the prevalence of vector sum saccades, we observed that the mean proportions of these responses declined as the age of subjects tested increased.