The Invisible Gorilla Is Smarter than You


Read the following question and remember the first answer that comes into your head: “How many animals did Moses take into the Ark?”

Did you think of pairs and were trying to work out a multiple of two, maybe trying to work out how many animal species there are? Or were you one of the few who knew this was a trick question and answered “zero,” as it was Noah and not Moses who had the Ark?

I’m currently reading three books which address problems like the one above where your mind can get fooled. They are The Invisible Gorilla: How Our Intuitions Deceive Us, You Are Not So Smart, and Thinking Fast and Slow. I Thinking Fast and Slow, Daniel Kahneman describes two modes that our brains can have – System 1 and System 2 thinking.

  • System 1 operates automatically and quickly with little or no effort — for example, if you see a horrible picture, your face reacts and shows your disgust.
  • System 2 allocates attention to the mental activities that demand it — for example, if you need to, you can focus on one voice in a noisy room.

All very interesting, but what use is this to a tester, for example?

Lots of uses.

The Invisible Gorilla awareness test is a classic (though now over-used) example of one of the biases (inattentional blindness) that can affect a tester. Give people a detailed test script to follow, and they will concentrate on the steps so much that they may well miss other issues.

Or take another example, Priming. A case study referenced in two of the books was where a group of people were given words that were to do with old age, when they left the room they were walking more slowly than when they walked in. If a developer hands over the latest version of the code and says it was hard to write and potentially buggy, will this make you test more intensively than if had said it was straightforward and all his tests had passed?

Then there is the Availability Heuristic — you are more likely to believe something is commonplace if you can find even one example of it. Do more words start with “r” or do more words have “r” as their third letter? Most people will say the former because it’s easy to think of many words that being with an “r,” but they would be wrong. Having to process words and think of the third letter is much harder, so the brain takes the easy option. If you’re brainstorming a new design or thinking of test ideas, do you come up with new ideas or variations on ones you know and use regularly?

Being aware of all these biases and how we think doesn’t mean they can all be overcome, but being aware can help us get the System 2 part of our thinking and make sure we’re not heading down the wrong path.

You Are Not So Smart and The Invisible Gorilla are are easy to dip into, with short quick chapters. Thinking Fast and Slow is a longer read. So work out which state your brain is in, and pick the appropriate book to read.