Three studies were conducted to determine whether differential patterns of categorization observed in studies using visual familiarization and object‐examining measures hold up as procedural confounds are eliminated. In Experiment 1, we attempted as direct a comparison as possible between visual and object‐examining measures of categorization. Consistent with previous reports, 9‐month‐old infants distinguished a basic‐level contrast (dog–horse) in the visual task, but not in the examining task. Experiment 2 was designed to reduce levels of nonexploratory activity in an examining task; 9‐month‐olds again failed to distinguish categories of dogs and horses. In Experiment 3, we adopted a paired‐comparison test format in the object‐examining task. Infants did display a novel category preference under paired testing conditions. The results suggest that the different patterns of categorization often seen in looking and touching tasks are a reflection, not of different categorization processes, but of the differential sensitivity of the tasks.

While very young children's understanding of objects as symbols for other entities has been the focus of much investigation, very little is known concerning the emergence of comprehension for symbolic relations among actions modeled with toy replicas and their real counterparts. We used videotaped depictions of real actions in a preferential looking task to assess toddlers' ability to comprehend such connections for action categories aligned with familiar object concepts. Across two experiments, 16- and 18-month-olds provided no evidence of understanding such relations, even when action categories were highlighted with verbal prompts. Among 24- and 26-month-olds, comprehension of relations between certain actions modeled with toys and videos of their real-world counterparts began to emerge, independent of expressive vocabulary size. Implications of our results for theoretical conclusions drawn from use of the generalized imitation procedure to study early conceptual development are discussed.

Two experiments are reported using a visual familiarization categorization procedure. In both experiments, infants were familiarized with sets of stimuli previously shown to contain asymmetric feature distributions that support an asymmetry in young infants' categorization of cats and dogs (i.e. infants' cat category excludes dogs but their dog category includes cats). In Experiment 1, the asymmetry was replicated in 4-month-old infants. In contrast, 10-month-old infants demonstrated exclusive category representations for both cats and dogs. In Experiment 2, an additional group of 10-month-olds demonstrated exclusive representations for both cats and dogs under conditions of very limited within-task category familiarization. Potential mechanisms underlying the shift from an asymmetric to a symmetric pattern of categorization in the first year are discussed.

From Aesop to Sun Tzu, the importance of working together has long been acknowledged. Yet as long as cooperation has existed, so have the difficulties associated with it. Pooling two fields might mean twice the power, but this union also brings twice the jargon, twice the competing theories, and twice the head butting. Nonetheless, in this collection, researchers have made a heroic effort to set aside their theoretical differences to produce three computational models for the influential set of empirical data showing that young infants have difficulty detecting correlations among features (Younger & Cohen, 1983, 1986). Specifically, Gureckis and Love (2004/this issue) fit a well‐developed adult‐learning model to the infant work (down to the exact order and number of test trials) in support of a common mechanism underlying categorization. Shultz and Cohen (2004/this issue) vary depth of processing in a cascade correlation network to show how older infants learn more than younger infants from the same amount of exposure. And Westermann and Mareschal (2004/this issue) introduce a model for their representational acuity hypothesis, which explains qualitative shifts as a decrease in the size of neural receptive fields. This commentary takes stock of this attempt at unifying computational modeling and developmental data by identifying common themes, clarifying points of disagreement, and providing a synthesis for this work.

We examined the influence of prior exposure to specific animal properties on 15-month-old infants' inductive generalization. Using picture books, 29 infants were trained on properties linked in a congruent or incongruent manner with four animal categories. A generalized imitation task was then administered to assess patterns of property extension for two of the trained properties as well as two untrained properties aligned with the training categories. Prior exposure to particular category-property relations was shown to impact infants' property extensions in that infants selected a novel member of the training category for their imitation. For untrained properties, infants selected equally between novel members of the training and non-training categories. The findings highlight the dynamic nature of inductive processes in infancy.