The capacity to represent the world in terms of numerically distinct objects (i.e., object individuation) is a milestone in early cognitive development and forms the foundation for more complex thought and behavior. Over the past 10 to 15 yr, infant researchers have expended a great deal of effort to identify the origins and development of this capacity. In contrast, relatively little is known about the neural mechanisms that underlie the ability to individuate objects, in large part because there are a limited number of noninvasive techniques available to measure brain functioning in human infants. Recent research suggests that near-IR spectroscopy (NIRS), an optical imaging technique that uses relative changes in total hemoglobin concentration and oxygenation as an indicator of neural activation, may be a viable procedure for assessing the relation between object processing and brain function in human infants. We examine the extent to which increased neural activation, as measured by NIRS, could be observed in two neural areas known to be involved in object processing, the primary visual cortex and the inferior temporal cortex, during an object processing task. Infants aged 6.5 months are presented with a visual event in which two featurally distinct objects emerge successively to opposite sides of an occluder and neuroimaging data are collected. As predicted, increased neural activation is observed in both the primary visual and inferior cortex during the visual event, suggesting that these neural areas support object processing in the young infant. The outcome has important implications for research in cognitive development, developmental neuroscience, and optical imaging.

Evidence indicating that sex-linked toy preferences exist in two nonhuman primate species support the hypothesis that developmental sex differences such as those observed in children's object preferences are shaped in part by inborn factors. If so, then preferences for sex-linked toys may emerge in children before any self-awareness of gender identity and gender-congruent behavior. In order to test this hypothesis, interest in a doll and a toy truck was measured in 30 infants ranging in age from 3 to 8 months using eye-tracking technology that provides precise indicators of visual attention. Consistent with primary hypothesis, sex differences in visual interest in sex-linked toys were found, such that girls showed a visual preference (d > 1.0) for the doll over the toy truck and boys compared to girls showed a greater number of visual fixations on the truck (d = .78). Our findings suggest that the conceptual categories of "masculine" and "feminine" toys are preceded by sex differences in the preferences for perceptual features associated with such objects. The existence of these innate preferences for object features coupled with well-documented social influences may explain why toy preferences are one of the earliest known manifestations of sex-linked social behavior.

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Recent research indicates that by 4.5 months, infants use shape and size information as the basis for individuating objects but that it is not until 11.5 months that they use color information for this purpose. The present experiments investigated the extent to which infants' sensitivity to color information could be increased through select experiences. Five experiments were conducted with 10.5-and 9.5-month-olds. The results revealed that multimodal (visual and tactile), but not unimodal (visual only), exploration of the objects prior to the individuation task increased 10.5-month-olds' sensitivity to color differences. These results suggest that multisensory experience with objects facilitates infants' use of color information when individuating objects. In contrast, 9.5-month-olds did not benefit from the multisensory procedure; possible explanations for this finding are explored. Together, these results reveal how an everyday experience-combined visual and tactile exploration of objects-can promote infants' use of color information as the basis for individuating objects. More broadly, these results shed light on the nature of infants' object representations and the cognitive mechanisms that support infants' changing sensitivity to color differences.

Over the past 30 years researchers have learned a great deal about the development of object processing in infancy. In contrast, little is understood about the neural mechanisms that underlie this capacity, in large part because there are few techniques available to measure brain functioning in human infants. The present research examined the extent to which near-infrared spectroscopy (NIRS), an optical imaging technique, could be used to assess the relation between object processing and brain functioning. Infants aged 6.5 months were presented with an occlusion event involving objects that differed on many feature dimensions (multi-featural change), differed on shape only (shape change) or color only (color change), or did not differ (control). NIRS data were collected in the occipital and inferior temporal cortex. In the occipital cortex, a significant increase in oxyhemoglobin (HbO(2)) was observed in response to all four events and these responses did not differ significantly from each other. In the inferior temporal cortex, a significant increase in HbO(2 )was observed in the multi-featural and the shape change condition but not in the control condition. An increase was also observed in the color change condition but this increase did not differ significantly from baseline nor did it differ significantly from the response obtained in the control condition. These data were discussed in terms of (a) what they suggest about the neural basis of feature processing in infants and (b) the viability of using NIRS to study brain-behavior relations in infants.