(repeat) Two heads may be better than one. But what about three or more? A new study shows that chimpanzees excel at complex tasks when they work in groups, and their accumulated knowledge can even be passed from one generation to the next.  But group-think also can be maladaptive. When humans rely on knowledge that they assume other people possess, they can become less than rational. Find out why one cognitive scientist says that individual thinking is a myth. Most of your decisions are made in groups, and most derive from emotion, not rationality. Also, why we know far less than we think we do. For example, most people will say they understand how an everyday object like a zipper works, but draw a blank when asked to explain it.  Plus, why we have a biological drive to categorize people as “us” or “them,” and how we can override it.   Guests:  Steven Sloman - Professor of cognitive linguistics and psychological sciences at Brown University and editor-in-chief of the journal, Cognition Robert Sapolsky - Professor of neuroscience at Stanford University and author of Behave: The Biology of Humans at Our Best and Worst Laurance Doyle - Scientist at the SETI Institute Learn more about your ad choices. Visit megaphone.fm/adchoices