Our June speaker, Christopher Chabris, is the co-author with Daniel Simons, of The Invisible Gorilla: How Our Intuitions Deceive Us.

The book (and his talk) discusses what he calls “everyday illusions” – intuitive commonsense beliefs about how our minds work, that often tend to be systematically wrong, hard to overcome, and can get us into big trouble if we’re not aware of them.

Chabris started with the question, can we really multi-task? He showed a video of a woman walking in a mall while fiddling with some electronic gizmo, and walking right into a water pool. A study on multi-tasking found there are actually some people who can do two things simultaneously with no loss of performance. But only one in forty.

The book’s title comes from an experiment, which Chabris conducted in the room by showing a video of six people passing a basketball around. Viewers were instructed to count the number of passes among the three white-shirted players. Because of that focus of attention, many viewers failed to notice the gorilla that walked among the players. (Or that the background drapes changed from red to gold.) This phenomenon he calls “inattentional blindness.”

Experimenters have found that even when some viewers’ eyes look directly at the gorilla, they still do not “see” it.

A real-life case involved a police officer chasing a suspect, who claimed he didn’t see a man being beaten up along the way. No one believed him; he was sentenced to prison for obstruction of justice. Chabris participated in an experiment designed to test a similar case, with students told to chase a person, and to focus their attention, to count how many times he touched his head. Even in daytime, 40% failed to see the three-person fight taking place along the route.

Thus, it’s an illusion that we will notice important things going on around us. Expectation is a key – often, we see what we expect to see. That wouldn’t include a gorilla strolling among basketball players.

Memory is similarly problematic. Most of us think our memories are detailed, accurate, and permanent. Not so. In truth, the brain doesn’t store much in memory, and when called upon essentially makes up a lot of it, filling in gaps. This is a serious problem in criminal justice, where eyewitness testimony looms large, and the system accords it a high degree of veracity. Big mistake.

Memory also operates by piecing together fragments from different parts of the brain. This could explain how Hillary Clinton famously mis-remembered coming under sniper fire in Bosnia; it was probably not an intentional fib.

Not only are we overly confident about our memory, the same is true of our intuitions, and our other abilities. Chabris takes a dim view of Gladwell’s book Blink, and the whole notion that we should trust our gut reactions and not over-think. He talked about the case of Madoff, who exuded such an air of confidence that investigators repeatedly were gulled.

So – is the conclusion that our brains are really crap, and maybe we should sue the so-called “intelligent designer” for malpractice?

Not at all. As Chabris pointed out, if we had to rationally think through every decision point throughout the day, we’d never get anywhere. Our brains are very good at making shortcuts, enabling us to navigate through the world, most of the time, pretty well. Though occasionally, those mental shortcuts do fail us, as when we overlook a gorilla in the room.