Acquiring generic knowledge without induction in infancy.

Children have been shown to generalize information acquired from social partners better when it is provided to them in a communicative manner. Two distinct learning mechanisms have been proposed to explain how communicative demonstrations assist the acquisition of generic knowledge in infants: by strengthening or speeding up inductive generalization processes (Boosted Induction), or by providing a direct generic statement in a nonverbal form (Nonverbal Generics), which makes additional generalization processes unnecessary. We sought to adjudicate between these accounts by exploring how children treat negative evidence, because disregarding negative evidence is considered to be a hallmark of having acquired generic knowledge. In two studies with 18-month-old infants, we tested the distinct predictions these two accounts offer on how infants should respond to experiencing a counterexample after acquiring information about a single object either from a communicative demonstration or from non-communicative observation. We found that the infants who learned a non-obvious property of an object from simple observation were discouraged from further generalizing this property after having encountered a counterexample. In contrast, the infants who received a communicative demonstration of the same property persisted in trying to elicit it from a novel exemplar even after they had failed to elicit it from a counterexample. These results support the Nonverbal Generics account, and suggest that human infants can learn generic knowledge directly, without induction, from others even before mastering the linguistic skills necessary for the comprehension of generic expressions.