This study examined the influence of shape similarity and labels on 13-month-olds' inductive inferences. In 3 experiments, 123 infants were presented with novel target objects with or without a nonvisible property, followed by test objects that varied in shape similarity. When objects were not labeled, infants generalized the nonvisible property to high-similarity objects (Experiment 1). When objects were labeled with the same noun, infants generalized the nonvisible property to high- and low-similarity objects (Experiment 2). Finally, when objects were labeled with different nouns, infants generalized the nonvisible property to high-similarity objects (Experiment 3). Thus, infants who are beginning to acquire productive language rely on shared shape similarity and shared names to guide their inductive inferences.

The role of words and gestures in guiding infants' inductive inferences about nonobvious properties was examined. One hundred seventy-two 14-month-olds and 22-month-olds were presented with novel target objects followed by test objects that varied in similarity to the target. Objects were introduced with a novel word or a novel gesture or with no label. When target and test objects were highly similar in shape, both 14- and 22-month-olds inferred that these objects shared a nonobvious property, regardless of whether the objects were labeled with a word or a gesture or with no label. When objects were labeled with the same word, both 14- and 22-month-olds generalized the nonobvious properties to objects that shared minimal perceptual similarity. Finally, when objects were labeled with the same gesture, 14-month-olds, but not 22-month-olds, generalized the nonobvious properties to objects that shared minimal perceptual similarity. These results indicate that 14-month-olds possess a more generalized symbolic system as they will rely on both words and gestures to guide their inferences. By 22-months of age, infants treat words as a privileged referential form when making inductive inferences.

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