Infant color vision: sharp chromatic edges are not required for chromatic discrimination in 4-month-olds

In our previous demonstrations of chromatic discrimination in infants, we have used test and surround fields of different chromaticities that abutted each other at sharp chromatic edges. In order to see whether sharp chromatic edges are necessary for infants to make chromatic discriminations, 16-week-old infants were tested with three stimulus configurations in which sharp chromatic edges were eliminated. The three edge manipulations involved black borders, a dark surround, or blurred edges around the chromatic test field. In each case red, green, and violet test fields were used. Although performance decreased when sharp chromatic edges were eliminated, observers' percent correct scores remained clearly above chance for eight of the nine discriminations (three colors x three edge manipulations). We argue that all three edge manipulations reduce the likelihood of mediation of chromatic discrimination by M (magnocellular) cells. These data thus provide evidence that young infants have functional P (parvocellular) pathways, and use them for making chromatic discriminations.