Visual complexity in infancy: contour or numerosity?

To examine the relationship between visual attention in infancy and the stimulus variables of contour and numerosity, 2- and 4-month-old infants were placed in 3 experimental conditions. In the first condition, the patterns shown to the infants varied in amount of contour but had an equal number of elements; in the second, they varied in numerosity but had an equal amount of contour; and in the third, the patterns varied in both numerosity and contour. The results showed that contour and numerosity acting in tandem are responsible for the age-complexity shift observed in previous investigations of infant attention.