Sometimes we don’t face that 800-pound gorilla in the room because we don’t notice him in the first place. This is what researchers Christopher Chabris and Daniel Simons proved in an experiment done 10 years ago.

In a video two groups, one group with white tee shirts, the other black, move randomly in a room while passing a basketball. The viewer’s task is to count how many passes the white-shirted members make. Halfway through the video, a woman dressed in a gorilla suit walks through the groups, stops, faces the camera, thumps her chest and walks off. Half of all viewers miss this. I did, and it left me unnerved.

Chabris and Simons have now written a book, "The Invisible Gorilla and Other Ways Our Intuitions Deceive Us" about all kinds of illusions we suffer from. We think we see things as they really are, but “our vivid visual experience belies a striking mental blindness,” they write.

They cover the illusion of memory, how often our memories are born from our own embellished stories; the illusion of knowledge, we think we know much more than we actually do; the illusion of cause, we quickly assume correlation means causation.

Such overestimations have profound consequences: eyewitnesses sending innocents to prison; believing—wrongly—that vaccines cause autism simply because of a correlation; or thinking we can text while driving. If there’s one thing we ought to take from watching the gorilla film it is that texting while driving is a ticking time bomb.

Perhaps the worst illusion of all, the failing that leads to others, is the illusion of confidence. We profoundly overestimate our ability to see things as they are. As the physicist Richard Feynman famously said: The first principle is you must not fool yourself, and you are the easiest person to fool.

—Christie Nicholson