A researcher into primate behavior has turned her Ph.D. thesis on Theory of Mind in chimpanzees into an engaging look at how we humans understand what is going on in each others’ minds. “Theory of Mind is the hallmark of humanity,” explains O’Connell, for it is the ability to understand that other people have thoughts, desires, and beliefs about the world, thus enabling us to handle complex social relationships and ultimately to develop a moral code. O’Connell, who writes for both academic journals and the popular press in England (the Guardian, the Observer, etc.) examines the nature of this ability and how its foundations are present in very young children and some animals. Her reports on studies with infants and children, which reveal the intermediate steps in the development of Theory of Mind, are fascinating, as are her descriptions of her own and other primatologists— work on the mental abilities of chimpanzees, baboons, gorillas, and other apes. We are shown how the ability to lie develops and how the power of the imagination leads to the evolution of empathy and compassion. What happens when Theory of Mind is missing or deficient is demonstrated in her discussions of research on autistic individuals and those with Asperger’s syndrome (often called high-functioning autistics, for they may be very intelligent, yet they are unable to show empathy and have poor social and communication skills). Moving on from living creatures to machines, O’Connell is willing to speculate on the possibility of building robots with minds. Her conclusion, supported by accounts of some robots under development, is that we may soon have robots with a simple version of Theory of Mind or perhaps robots that, in a limited context, act as if they have it. Both highly readable and enlightening’science made simple, not simplistic.