The Invisible Gorilla: A Classic Experiment in Perception

05 June, 2020
The invisible gorilla experiment surprises everyone who hasn't heard about it before. Its results show how our selective attention works and the mistakes we can make with it.

The invisible gorilla experiment has become a psychology classic. Although it was conducted for the first time in 1999, it’s still cited as a typical example of the limitations of perception. It also illustrates how people don’t like to accept the fact that they’re often blind to the world around them.

The creators of the invisible gorilla experiment, Christopher Chabris and Daniel Simons, never imagined that this experiment would awaken so much curiosity and become so popular. It’s been replicated countless times, in different countries and with people of all ages and educational levels, with very similar results.

If you want to do the experiment yourself, just watch the following video and follow the instructions, before you continue reading. The rest of the article will make more sense if you do!

  • Just count the number of passes that the white shirt team makes to each other.
  • You have to be attentive and take into account both the air passes and the bounce passes.
  • Do the test. Then, continue reading.

The invisible gorilla experiment

A couple of paragraphs above, we gave you the same instructions that Chabris and Simons gave to a group of student volunteers before doing the experiment.

When the participants finished watching the video, they were asked the following questions (answer them as well if you watched the video):

  • “Did you notice anything unusual while counting the passes?”
  • “Did you notice anything else besides the players?
  • “Or did you notice anyone other than the players?”
  • “Did you notice a gorilla?”

The last question was the one that surprised the volunteers of the invisible gorilla experiment the most. At least 58% of them. Whenever the experiment has been repeated, the percentage of surprise is more or less the same. Yes, there was a gorilla in the video, but more than half of the people didn’t notice it. Did you see it?

The reactions to what happened

The first time the invisible gorilla experiment was conducted, and all subsequent ones, most of those who participated and didn’t notice the presence of the gorilla were amazed at how clear it all was! It seemed impossible to them that they had overlooked something so obvious.

When they’re asked to watch the video again, they all see the gorilla without a problem. Some think that they’ve been shown two different videos, but, of course, this isn’t the case. This experiment won the Ig Nobel Prize. This is an award given to those scientific activities that “first make you laugh and then make you think”.

Why are so many people blind to such an obvious image in the video? That’s the big question that comes out of this. It’s also striking that so many people refuse to accept that their eyes and perception are deceiving them. They think they’re seeing everything correctly, and yet they haven’t seen something so obvious.

A blindfolded woman.

The traps of perception

Researchers Steve Most and Robert Astur conducted a similar experiment years later. In this case, a driving simulator was used. The volunteers were told that when they reached a junction they should stop if they saw a blue arrow. However, if they saw a yellow area, they didn’t have to stop.

However, when the volunteers were performing this activity, two motorcycles passed in front of them in the simulator. When the motorcycle was blue, the virtual drivers noticed it and braked. When it was yellow, almost 60% hit the rider. Somehow, the results of the invisible gorilla experiment were replicated.

What happens in these cases is that people focus their attention only on the point that interests them. In the first case, on the white team’s passes, and in the second case, on the blue arrow. In their mind, they focused all their attention on the color. Since the gorilla was black and some of the motorcycles were yellow, the volunteers didn’t notice that element.

This is because some people can only focus on one variable at a time, whereas others have a wider and more flexible attention pattern. For example, this is why you should never speak on the phone when you’re driving.

Chabris, C. F., Simons, D. J., & Ferrari, G. (2011). El gorila invisible y otras maneras en las que nuestra intuición nos engaña. Siglo Veintiuno Editores Argentina.