  In a seminal paper of 1978, Premack and Woodruff posed the question of whether chimpanzees have a ‘theory of mind’; that is, do they attribute mental states to others, and do they, like adult humans, predict and explain action on the basis of hypotheses about these states. It was a mark of Piaget’s influence that no one had as yet asked this question in regard to human infants; Piaget thought that they did not yet have a robust notion of an external world at all, let alone of a world containing minds.  The chimp studies led to an explosion of research into the development of a theory of mind in human beings. In responses to Premack and Woodruff’s paper, Dennett and others commented that the successful prediction of another’s action does not yet constitute evidence for a theory of mind. Consider the following: a child participant in a study is told a story about a boy named Max who has a piece of candy. Max puts it into the red cabinet and goes out to play in the yard. The child participant is asked, “When Max returns and wants to get his candy, where will he look for it?” The child might answer correctly because he or she understands that Max will think that the candy is where he left it or last saw it (i.e., the red cabinet). This involves attributing mental states to Max. But the child might also answer correctly because that’s where the candy actually is. That is, the child with no theory of mind might still answer correctly simply by reasoning that people go to get things where they are. The way to resolve this uncertainty, Dennett proposed, was the false belief task. In this task, which quickly became the litmus test of a theory of mind, the story includes a second character who enters the scene while Max is still outside in the yard. This second character finds the candy in the red cabinet and puts it into the yellow cabinet. Once again, the child participant—who has seen the transfer—is asked where Max will look for his candy when he returns to the kitchen. Only if the child is successful now, responding that Max will look in the red cabinet—even though the child knows that the candy is really in the yellow cabinet—can we legitimately attribute to the child a theory of mind. There is now a very large literature involving the false belief task and the bottom line appears to be that most young 3-year-olds incorrectly predict that Max will look in the yellow cabinet (or, in some studies, say that Max thinks it’s in the yellow cabinet) because that’s where it is, while somewhere between the ages of 3.5 and 4, children begin to succeed on the  task.[24]