Object individuation in infancy: the value of color and luminance
Woods, Rebecca Jindalee
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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 until 11.5 months. However, color and luminance frequently co-vary in the natural environment, and color and luminance interact in pattern detection, motion detection, and stereopsis. 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, Experiments 1 and 2 assessed 7.5-month-old infants? ability to individuate uniformly colored objects that either varied in both color and luminance or varied in luminance alone. The results indicated that infants used these features to individuate only when the objects varied in both color and luminance. Thus, when color and luminance co-varied, infants used these features to individuate objects a full 4 months earlier than infants use either feature alone. Experiment 3 further explored the link between color and luminance by assessing 7.5-month-old infants? ability to use pattern differences to individuate objects. Although infants use pattern differences created from a combination of luminance and color contrast by 7.5 months, results from Experiment 3 indicated that when pattern was created from either color contrast or luminance contrast alone, infants fail to individuate based on pattern. The results of Experiment 3 suggest that it is not the number of feature dimensions that is important, but the unique contribution of both color and luminance that is particularly salient to infants. 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.