Do monkeys have a theory of mind?

The new issue of Smithsonian magazine profiles the work of Yale psychologist Laurie Santos, 32, who hangs out with monkeys on an island off the coast of Puerto Rico to get inside their heads. She draws from cognitive neuroscience and evolutionary psychology to suss out whether these non-human primates have a "theory of mind." The "theory of mind" refers to the ability to recognize and understand others' thoughts, desires, intentions, and feelings--basically to get where someone else if coming from. Santos tries to show that monkeys have this cognitive capacity. The article presents several of her field experiments and the results. From Smithsonian:
"This is what we do," (Santos) says, "hike around looking for monkeys by themselves who are hungry and want to play. It's hard to find social creatures by themselves," she adds as she backs out of the field of view of a primatologist's video camera, "and even harder to find ones that aren't being followed by other researchers..."

Santos' interest here is in what psychologists call "theory of mind," the ability to impute thoughts and intentions to another individual, one of the cornerstones of human cognition. "Sitting here talking with you," Santos explains, "all I can see is your behavior, but I draw inferences about your desires and thoughts. The interesting question is, how far back in evolutionary time does that ability extend? Can it exist without language?" As recently as a decade ago, the conventional wisdom doubted that even chimpanzees, which are more closely related to human beings than are monkeys, possessed theory of mind. This view is changing, in large measure because of the work of Santos and her collaborators. With her students in tow and a small bag of grapes in her pocket, Santos is now out to demonstrate the phenomenon–if a Macaca mulatta can be induced to cooperate.
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