Most of us would agree that there's a clear--and even obvious--connection between the things we believe and the way we behave. But what if our actions are driven not by our conscious values and beliefs but by hidden motivations we're not even aware of? The "hidden brain" is Shankar Vedantam's shorthand for a host of brain functions, emotional responses, and cognitive processes that happen outside our conscious awareness but have a decisive effect on how we behave. The hidden brain has its finger on the scale when we make all our most complex and important decisions: It decides whom we fall in love with, whether we should convict someone of murder, and which way to run when someone yells "Fire!" It explains why we can become riveted by the story of a single puppy adrift on the ocean but are quickly bored by a story of genocide. The hidden brain can also be deliberately manipulated to convince people to vote against their own interests, or even become suicide terrorists. But the most disturbing thing is that it does all this without our knowing. Shankar Vedantam, author of The Washington Post's popular "Department of Human Behavior" column, takes us on a tour of this phenomenon and explores its consequences. Using original reporting that combines the latest scientific research with compulsively readable narratives that take readers from the American campaign trail to terrorist indoctrination camps, from the World Trade Center on 9/11 to, yes, a puppy adrift on the Pacific Ocean, Vedantam illuminates the dark recesses of our minds while making an original argument about how we can compensate for our blind spots--and what happens when we don't.