Of Bacteria and Men: The Invisible Gorilla by Chabris and Simons

The invisible gorilla and other ways ourintuition deceives us, by psychologists Christopher Chabris and Daniel Simons, is a wonderful book that contains a lot of food for thought for scientists – and actually for everybody.

There is little chance that you missed this viral video, dating back from just before the turn of the millennium: two teams, dressed either in white or in black, play basketball, and you are supposed to count how many passes the white team manages to do. If you never saw that, watch it here before reading. OK, that was the one and only spoiler alert!

In the middle of the video, a student wearing a gorilla suit walks through the players, thumps her chest, and leaves. I didn’t see the gorilla, just as half of the people who watch the video, because I was too focused on counting the white team passes. With this video, Chabris and Simons showed us that we wrongly take certain things for granted, such as our ability to notice everything that enters our field of view. They write in their introduction (p. ix):

“We all believe that we are capable of seeing what’s in front of us, of accurately remembering important events from our past, of understanding the limits of our knowledge, of properly determining cause and effect. But these intuitive beliefs are often mistaken ones that mask critically important limitations on our cognitive abilities.”

In addition to discussing the “illusion of attention” (our false belief that we should have noticed the gorilla), the book covers five other common illusions to which we fall prey: memory, confidence, knowledge, cause and potential.

All these illusions exist because we most often misunderstand the way our brain works. What hides inside of our skull is no sophisticated computer that “saves” all kinds of information on some kind of “hard drive”. Actually, scientists and philosophers are still struggling to understand what it is exactly that the brain does. But it seems to be a highly dynamic processing machine, which constantly integrates information to build a useful picture of our surrounding world.

Memory is particularly treacherous, as our memories evolve and are transformed with time, without necessarily losing of their veracity feeling. (This can lead to amazing memory mistakes: the authors bring the story of Hilary Clinton remembering a mission to Bosnia, and its heavy consequences on her 2008 campaign.)

Of specific interest for scientists are the so-called “illusion of knowledge” and “illusion of cause”. As to knowledge, it is our tendency to believe that we understand more than we actually do. The illusion of knowledge can be dramatically exemplified in fund traders, who believe they “understand” the market and the forces that govern it, whereas most of the time their gains or losses are just due to chance. As to cause, the mistake is to believe that when two events happen together, one must have caused the other; for scientists, this translates into the popular catchphrase correlation does not imply causation.

Overall, the invisible gorilla makes for a very engaging and inspiring book, even though it (sometimes painfully) points out how limited we human beings can be. The lesson is clear: we have to better understand the way our cognitive system works to avoid these powerful illusions. This is enlightening.

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