Several recent studies have revealed substantial limitations in 2‐year‐olds' ability to search accurately for objects that have undergone unseen movement, even along highly constrained paths. In many of these studies, children observed a ball as it rolled down a track and behind an occluding panel that contained 4 doors. The track had a barrier that was partly visible and could be placed in locations corresponding to the doors. When the ball came to a rest against the barrier and behind the occluder, the child's task was to find the ball by opening the correct door. The search accuracy of 2‐year‐olds has not differed from chance across several variations of this task. This research was conducted to identify the source of 2‐year‐olds' limitation in this domain. Children were granted a full view of the event before the ball was occluded with a door panel. Children's performance was better under this condition, but was still not systematically accurate unless their gaze remained locked onto the correct location. Two‐year‐olds' weak performance in these search tasks appears to be more a consequence of limitations in spatial integration than in their representation of unseen movement.

What processes do infants employ in categorizing? Infants might categorize on line as they encounter category-related entities; alternatively, infants might depend on prior experience with entities in formulating categories. These alternatives were tested in forty-four 5-month-olds. Infants who were familiarized in the laboratory with a category of never-before-seen objects subsequently treated novel objects of the same category as familiar --they categorized on line --just as did infants who were exposed to objects from the same category at home for 2 months leading to their laboratory assessment of object categorization. Infants with home experience also recognized novel category objects as familiar from the outset -that is, prior experience with category exemplars was brought to bear in laboratory tasks.

Five-month-old infants of nondepressed and clinically depressed mothers were habituated to either a face with a neutral expression or the same face with a smile. Infants of nondepressed mothers subsequently discriminated between neutral and smiling facial expressions, whereas infants of clinically depressed mothers failed to make the same discrimination.

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This study examined infants' use of object knowledge for scaling the manipulative force of object-directed actions. Infants 9, 12, and 15 months of age were outfitted with motion-analysis sensors on their arms and then presented with stimulus objects to examine individually over a series of familiarization trials. Two stimulus objects were used in the familiarization phase, and were identical in size, shape, and material, but different in color and weight. Following familiarization, two test objects that had been hidden from view were presented. The test objects were identical in appearance to the familiarization objects, but their color-weight correspondence was reversed. Infants' actions on the test objects revealed selective, differential preparation for the specific weights experienced during familiarization. Because the objects were equivalent in their visual affordances for action, the differential preparation and coordination of manipulative force was based on knowledge acquired during the familiarization phase. Infants are capable of utilizing object representations to coordinate manipulative force in object-directed actions.Send correspondence to Clay Mash, NICHD,