Abstract
In order to investigate potential effects of visual experience vs. preprogrammed mechanisms on visual development, we have investigated how well variation in contrast sensitivity (CS) across a large group of typical infants (n = 182) can be accounted for by a variety of factors that differ in the extent to which they are tied to visual experience. Using multiple regression analyses, we find that gestational length and gender, which are unlikely to be tied to visual experience, predict Luminance CS (thought to be mediated by the Magnocellular pathway). Other factors, which might be tied to either preprogrammed mechanisms or visual experience, specifically, birth order and small variations in postnatal age, predict Chromatic CS (thought to be mediated by the Parvocellular pathway) and Luminance CS. In addition, we have investigated effects of visual experience vs. preprogrammed mechanisms by studying CS in infant twins (n = 64). Our results show that the CS of both monozygotic (Mz) and dizygotic (Dz) twin pairs are significantly correlated with one another (accounting for ∼35% of the variance in CS), which could be due to either shared environment or genetic preprogramming. More data will allow us to determine whether correlations are significantly stronger in Mz vs. Dz twins, which would provide direct evidence of effects of genetic preprogramming. Based on our multiple regression studies (above), as well as our studies of premature infants (presented in this symposium), we predict that genetic preprogrammimg will be more influential for Luminance (Magnocellular pathway) CS than Chromatic (Parvocellular pathway) CS.