This study examined behavioral correlates of the rapid central nervous system changes occurring in the first 4 months of life. It was hypothesized that during the early months of infancy, visual preference would occur as a function of quantitative dimensions of the stimuli (size) which could be mediated at a subcortical level. It was further hypothesized that when primitive reflex measures showed a diminution, thus signifying integration between cortical and subcortical structures, visual preference should shift to qualitative stimulus dimensions (curved versus straight elements) mediated at a cortical level. Sixteen infants participated in the behavioral study, in which they were tested at home seven times: at 2, 5, 8, 11, 13, 15, and 17 weeks of age. One of these infants also had his EEG measured seven times during the first 3 months of his life. Visual fixation of all infants was compared for five sizes of a bull's-eye pattern paired with an intermediate-sized horizontally striped pattern, and five sizes of the striped pattern paired with the intermediate-sized bull's-eye pattern. On the same day that visual behavior was assessed, the strength of seven reflexes was measured. Results showed that all of the primitive reflexes were present and normal or strong in the 2-week testing and weak or absent by the 17-week testing. Findings also showed that while young infants clearly had a preference for larger stimuli, their fixation preferences by 8 weeks of age seemed determined much less by the size of the stimuli, and they clearly showed a preference for curvature by the time they were 11 weeks old. (JMB)