A competition model of exogenous orienting in 3.5-month-old infants.

Four experiments are reported on exogenous (stimulus-driven) orienting in 3.5-month-old infants. A small moving bar embedded in a field of static bars was used to draw the infant's attention to one side of the display or the other. The bars could be either red or green. In all four of these experiments sensitivity to this small moving bar was affected significantly by how unevenly the red and green bars were distributed across the visual field. Sensitivity to the moving bar was lower when most of the red bars were in the field contralateral to this probe suggesting competition between the motion stimulus and contralaterally placed red but not green bars on a small, but significant proportion of trials. This basic effect replicated in four separate experiments and depended coarsely on how unevenly the red and the green bars were distributed across the field. A competition model of exogenous orienting with a winner-take-all rule captured the most important features of the data. The distribution of color within the visual field can bias attention significantly at 3.5 months making it either more or less likely that an infant will detect a moving stimulus. Copyright 1998 Academic Press.