previously planned sequences rather than to compute new and context-sensitive sequences. Interestingly, at each stage infants show themselves able to evaluate correct sequences even when they cannot generate them. Specifically, infants can identify correct sequences for the retrieval of a hidden object long before they spontaneously produce these sequences. Similarly, infants can identify context-appropriate searches after delays of 15, 30, and even 70 seconds long before they produce correct searches at comparable delays.
A salient aspect of the explanations proposed here is that they appeal to problem solving limitations that have already been identified in children and adults. Adults often have difficulty solving physical problems whose solutions depend on moves that are counterintuitive in that they appear to take one farther away from one's goal. Furthermore, adults can be lulled by overall context similarity in applying a previous solution that is no longer appropriate. Finally, in all these instances, adults typically have little difficulty recognizing accurate solutions, even when they have failed to generate them.
The general picture suggested by the present research is, thus, one in which the physical world of infants appears very similar to that of adults: Not only do infants and adults share many of the same beliefs and show many of the same physical reasoning abilities, but these abilities seem limited in the same ways.
The research presented in this chapter is interesting for three reasons. One is that it yields a picture of infants as budding intuitive physicists, capable of detecting, interpreting, and predicting physical outcomes, which is radically different from the traditional portrayal of young infants as enclosed within a world in which an object is "a mere image which reenters the void as soon as it vanishes, and emerges from it for no objective reason" ( Piaget, 1954, p. 11). Another reason is that it suggests several new directions for research on infants' acquisition and representation of physical knowledge and on the manifestation of this knowledge in tasks calling for manual and non-manual responses. The third reason is that, as we discover how infants attain, represent, and use physical knowledge, we come one step closer to understanding the central issue of the origins of human cognition.
The research reported in this manuscript was supported by grants from the National Institute of Child Health and Human Development (HD-21104 and HD-05951). I wish to thank Judy Deloache and Carl Granrud for their careful and discerning review of the manuscript, and Jerry DeJong and Joe Malpelli for insightful suggestions about the research.