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Book review: Six intuitions you shouldn鈥檛 trust

The 鈥済orilla in our midst鈥� psychology experiment is up there among the world鈥檚 most famous. But as Liz Else found out from Christopher Chabris and Daniel Simons, the psychologists who devised it, exactly how it fools half of the people who take part is still a mystery

How did you come up with the experiment?

Christopher Chabris: We didn鈥檛 say, 鈥渓et鈥檚 do a really intriguing experiment people will talk about for years鈥�. It was just a class project on visual attention in a course we were teaching 12 years ago. The gorilla suit was lying around in a lab. If it hadn鈥檛 been there, who knows?

Daniel Simons: Our study revisited work from the 1970s by , where subjects had to watch a video and count the times players passed a ball. Neisser had someone with an open umbrella walk through the game, and many people didn鈥檛 notice it. But his which gave people an excuse for missing the person with the umbrella. We filmed the entire game with a single camera so that everything was fully visible 鈥� and the person in the gorilla suit was there for 9 seconds! When we showed the video, only half of the viewers saw the gorilla.

Is it the same for every group?

DS: The first subjects were Harvard University students but it worked as well with everyone we tested. For years, whenever I showed the video, I held my breath, thinking everybody would notice it. It took years before I could discount that gut instinct. Missing the gorilla is jarring. It鈥檚 natural to assume that you would see it, so it鈥檚 surprising and compelling when you realise what you鈥檝e missed.

So why do people miss the gorilla?

CC: It鈥檚 like a Rorschach (inkblot) test for cognitive abilities or personality: people think there must be something different about the people who see the gorilla compared with those who don鈥檛. Some speculate that if you are in a detail-oriented job, you are going to notice it because you notice everything, or you are not going to notice it because you are really good at focusing. But the truth is, so far no researcher has found anything that solidly predicts who is going to see it and who is not.

DS: We have looked at basic measures of attention and memory 鈥� how much you can hold in mind while doing something else, and how much you can take in with one attentional glance. These basic measures predict how well you can focus attention and count the passes, but they don鈥檛 seem to predict whether you will notice the gorilla. I have just done a , which I showed to about 1000 vision scientists who knew about the original video. As the gorilla enters, I introduced two changes: a backdrop curtain changes from red to gold, and one player wearing a black shirt leaves the court. The vast majority missed both, despite knowing the video was about unexpected objects. When they started looking for a gorilla, they missed other unexpected events.

鈥淚f we were aware of our limitations, we wouldn鈥檛 text while driving鈥�

Is there an evolutionary reason to miss things?

DS: I think that鈥檚 the wrong way around. These failures of awareness are more a consequence of something that we need to do and that we do well 鈥� focus attention. To do any task, you need to focus on things that matter and avoid things that don鈥檛. One consequence is that sometimes you filter out things you might want to see. Intuitively we think that things that matter will catch our attention, but they don鈥檛.

CC: In our book (reviewed on CultureLab) we tell the story of a Boston police officer chasing a suspect. When you do that, you鈥檙e paying careful attention, figuring out where he鈥檚 going, if he鈥檚 got a gun or is throwing evidence away. The officer ran past an incident of police brutality taking place close by and later claimed not to have seen it. He went to prison because the jury didn鈥檛 realise the extent to which focusing on one task makes you unable to see outside that. They decided he lied to protect fellow officers.

So our picture of reality can be very wrong?

DS: Our picture of reality is correct most of the time for most of what we do. It is inherently incomplete, though, and most of the time we don鈥檛 realise how much we miss. Usually, it doesn鈥檛 matter 鈥� we see what鈥檚 relevant to what we鈥檙e doing. It鈥檚 important to know that we have such limitations, though. We think we see more than we do, and that has consequences. We also think our memories are more perfect than they are, that we understand complex systems better than we do. If we were aware of our limitations, we wouldn鈥檛 text and drive or think everybody who mis-remembers is lying.

Can you devise another experiment this good?

CC: The statistics are against it! But who knows what we鈥檒l find lying around tomorrow鈥�

Book review: Six intuitions you shouldn鈥檛 trust