A tendency that predates humanity--Author Tali Sharot didn’t expect to stumble on something like the optimism bias while she was researching how traumatic events create “flashbulb memories”, which are unusually vivid memories that as it turns out are often not as accurate as they feel. Why would our brains construct intensely striking memories of harrowing events--like the terrorist attacks of September 11, 2001--that are not completely true accounts of what happened? While trying to answer that question Sharot conducted an experiment recording people’s brain activity as they remembered an event in the past and imagined one in the future, but the strange results she got sidetracked her. Every time people were asked to picture a future event, no matter how mundane, they came up with excessively rosy scenarios. People seemed to have a powerful and automatic tendency to imagine an unreasonably bright future. After switching her research focus to optimism Sharot concludes, and argues in this book, that optimism is so important to our survival that the inclination toward it is “hardwired” into our brains. Besides protecting us from stress and worry, optimism can become a self-fulfilling prophecy. Though people with an overly pessimistic vision might just give up, people with a helpful level of optimism believe a sunny future is attainable and they’ll work for it. Optimists act in ways that make their rosy predictions more likely to happen.Interestingly, it’s not just humans who are optimistic. Experiments conducted on many animals, including primates, suggest optimism is a very old evolutionary adaptation. I don’t think of myself as an optimistic person so I wasn’t expecting to see much of myself in the book’s examples, but as I read I had to admit I am more influenced by this tendency than I would have guessed. At least I’m not alone. Even given facts and figures most people still underestimate the likelihood of experiencing negative events like becoming ill with disease, being the victim of a crime or going through a divorce. Way more than half of us think we are above average in friendliness, leadership qualities, or common sense, etc., and, of course, statistically many of us have to be wrong in those assumptions. The book is full of lots of examples of how we don’t perceive the world quite as accurately as we think we do, for instance most people are not good judges of what actually makes us happy. Also covered are why hard times often increase group optimism, why we value things more after we chose them (monkeys do this too), and how much dread and anticipation change our experiences of events. Especially illuminating for me was the chapter on the causes and treatment of depression.