Covariation of color and luminance facilitate object individuation in infancy

Abstract

The ability to individuate objects is one of our most fundamental cognitive capacities. Recent research has revealed that when objects vary in color or luminance alone, infants fail to individuate those objects until 11.5 months. However, color and luminance frequently covary in the natural environment, thus providing a more salient and reliable indicator of distinct objects. For this reason, we propose that infants may be more likely to individuate when objects vary in both color and luminance. Using the narrow-screen task of Wilcox and Baillargeon (1998a), in Experiment 1 we assessed 7.5-month-old infants' ability to individuate uniformly colored objects that varied in both color and luminance or luminance alone. Experiment 2 further explored the link between color and luminance by assessing infants' ability to use pattern differences that included luminance or color to individuate objects. Results indicated that infants individuated objects only when covariations in color and luminance were used. These studies add to a growing body of literature investigating the interaction of color and luminance in object processing in infants and have implications for developmental changes in the nature and content of infants' object representations.

Figure 1

Schematic drawing of the green–red familiarization and test events seen in Experiment 1. Infants first saw the familiarization event (A). After the familiarization event, infants saw either a narrow- or a wide-screen test event (B). The orange–purple condition of Experiment 1 and the luminance contrast and color contrast conditions of Experiment 2 were identical to those in the green–red condition except that the green and red balls were replaced with the balls appropriate for each condition.

Figure 2

Bird's-eye view of the testing situation.

Figure 3

Mean looking times (in seconds, with standard error bars) of the 7.5-month-olds in Experiment 1 during the familiarization and test trials. Asterisks represent significance at α ≤ .05.

Figure 4

Mean looking times (in seconds, with SE bars) of the 7.5-month-olds in Experiment 1, additional results during the familiarization and test trials.

Figure 5

Rendering of the dotted and striped balls used in Experiment 2 and in Wilcox (1999), Experiment 3A. In Experiment 2, patterns were created by color alone (color-contrast condition) or luminance alone (luminance-contrast condition), whereas in Wilcox (1999), patterns were created using both color and luminance contrast. Color photographs are available in the supplemental materials to this article.

Figure 6

Mean looking times (with standard error bars) of the 7.5-month-olds in Experiment 2 during the familiarization and test trials.