Behind the scenes of the “gorilla experiment”

The title of The Invisible Gorilla refers to an experiment that Dan and I conducted at Harvard in the late 1990s. In the first part of Chapter 1 (which you should be able to read soon when we post an excerpt on our site), we mention that the idea arose originally as an exercise for a course that Dan was teaching and for which I was the teaching fellow (Harvard’s special name for “teaching assistant”). The course was a “laboratory methods” course in which students learned how to conduct experiments in cognitive psychology. Over the semester, each student worked on his or her own individual project, but Dan wanted to have at least one group project that everyone could be involved in. So most of the people passing basketballs as well as the gorilla walking through the action were students who were in the course at the time.

The experiment was inspired by research done by Ulric Neisser in the 1970s. Neisser had a woman carrying an umbrella walk across a basketball court. We filmed several different versions of the video originally, using both an umbrella woman and a gorilla. Those involving the gorilla had it just walk through the action without stopping in the middle, which took about five seconds. The video that has become popular was actually an afterthought. We had finished what we planned to do for our experiment, but we had more time (and tape, and students) available, so we tried a few other strange things, like having players exit and re-enter the action, even by calling the elevator and getting in. For fun, we tried a version in which the gorilla stops in the middle of the action, turns toward the camera, and thumps its chest before exiting. We weren’t even sure whether we could pull it off without the ball or the players hitting into the gorilla, but it worked on the first take.

Once we ran the main experiment (with the non-thumping gorilla videos), we tried the “thump” video to see if people would still miss the gorilla even with it on screen for nine seconds, almost twice as long as the original five seconds. To our own surprise, it worked just as well, and produced the even more dramatic demonstration of inattentional blindness.

The original report of our findings is in the article “Gorillas in Our Midst,” published in the journal Perception in 1999.

You can view the video itself on Dan’s lab website.

Comments are closed.