Rebecca Saxe has an essay in the current Boston Review entitled "Reading Your Mind: How our brains help us understand other people":
Children's early understanding of what makes people do the things they do appears to develop in two stages. In the first stage, children understand that people act in order to get the things they want: that human beings are agents whose actions are directed to goals. ...
Children in the first stage are missing something very specific: the notion of belief. Until sometime between their third and fourth birthdays, young children seem not to understand that the relationship between a person's goals and her actions depends on the person's beliefs about the current state of the world. ...
An impressive conceptual change occurs in the three- or four-year-old child.... a ... transition from the first stage of reasoning about human behavior, based mainly on goals or desires, to the richer second stage, based on both desires and beliefs.
This cartoon (by Dan Zettwoch, based on a story by Jason Shiga) shows how difficult -- and important -- such reasoning can be. As I wrote a few months ago, the cartoon has a special force for anyone who has ever tried to work these calculations out in explicit, logical terms.
Once you get past the stereotyped formulae, to participate effectively in a conversation requires making and re-making plans and predictions about how your actions will affect your interlocutors' states of mind. Even tracking the conversations of others involves lots of inferences about other people's desires and beliefs, and the half-conversations that cell phone users impose on us may be obnoxious because we have to "read minds" with only half the normal evidence.
It seems likely that this ability to "read minds" -- and to plan to change minds -- is a critical piece of the evolutionary history of language, and perhaps a rather recent one. A 1998 review article by C.M. Heyes entitled "Theory of Mind in Non-Human Primates" concludes that
A survey of empirical studies of imitation, self-recognition, social relationships, deception, role-taking and perspective-taking suggests that in every case where nonhuman primate behavior has been interpreted as a sign of theory of mind, it could instead have occurred by chance or as a product of nonmentalistic processes such as associative learning or inferences based on nonmental categories.
Saxe describes some recent experiments by Brian Hare, which suggest that chimps can reason about other chimps' mental states "in a competitive setting where some natural benefit follows from knowing what the other chimpanzee believes", though she also says that "[t]here is another way for the subordinate chimp to solve the competitive problem, one that depends only on certain behavioral associations, and not on ideas about beliefs at all."
Neither Saxe nor Heyes discusses parrots.
Posted by Mark Liberman at February 18, 2004 07:46 PM