The phrase, "the invisible gorilla," comes from an experiment created 10 years ago to test selective attention. In it, study participants are asked to watch a video in which two teams, one in black shirts and one in white shirts, are passing a ball. The participants are told to count how many times the players in white shirts pass the ball.
CONAN: And you both created your invisible gorilla experiment over 10 years ago to test what's called inattentional blindness. And I know I've sort of simplified the experiment a little bit, but what seems to be interesting is not that half the people don't notice it when they're supposed to be counting the number of passes made by the white team, but that indeed, even after they're certain they couldn't have missed it.
Mr. SIMONS: Well, essentially. That study was a follow-up to the original one, and rather than using basketball players and a gorilla going through the scene, we simplified it so we could have a little bit more control. And this was a study done by my former student, Steve Most(ph).
The Invisible Gorilla is a book published in 2010, co-authored by Christopher Chabris and Daniel Simons. This title of this book refers to an earlier research project by Chabris and Simons revealing that people who are focused on one thing can easily overlook something else. To demonstrate this effect they created a video where students pass a basketball between themselves. Viewers asked to count the number of times the players with the white shirts pass the ball often fail to notice a person in a gorilla suit who appears in the center of the image (see Invisible Gorilla test), an experiment described as "one of the most famous psychological demos ever".[1] Simons and Chabris were awarded an Ig Nobel Prize for the Invisible Gorilla experiment.[2]
A dumbfounding study roughly a decade ago that many now find hard to believe revealed that if people are asked to focus on a video of other people passing basketballs, about half of watchers missed a person in a gorilla suit walking in and out of the scene thumping its chest.
Of course, these results are utterly counterintuitive, with 90 percent of people now predicting that they would notice the gorilla in the video. The problem is that this video has become so famous that many people know to look for a gorilla when asked to count basketball passes.
"You can make two competing predictions," Simons said. "Knowing about the invisible gorilla might increase your chances of noticing other unexpected events because you know that the task tests whether people spot unexpected events. You might look for other events because you know that the experimenter is up to something." Alternatively, "knowing about the gorilla might lead viewers to look for gorillas exclusively, and when they find one, they might fail to notice anything else out of the ordinary."
Of the 41 volunteers Simon tested who had never seen or heard about the old video, a little less than half missed the gorilla in the new video, much like what happened in the old experiments. The 23 volunteers he tested who knew about the original gorilla video all spotted the fake ape in the new experiment.
However, knowing about the gorilla beforehand did not improve their chances of detecting other unexpected events. Only 17 percent of those who were familiar with the old video noticed one or both of the other unexpected events in the new video. In comparison, 29 percent of those who knew nothing of the old video spotted one of the other unexpected events in the new video.
The video depicts six actors passing a basketball. Viewers are asked to count the number of passes. Many people are so intent on counting that they fail to see a person in a gorilla suit stroll across the scene, stop briefly to thump their chest, and then walk off.
The Utah study began with 306 psychology students who were tested with the gorilla video, but about one-third then were excluded because they had prior knowledge of the video. That left 197 students, ages 18 to 35, whose test results were analyzed.
Next, the participants watched the 24-second Chabris-Simons gorilla video, which had two, three-member basketball teams (black shirts and white shirts) passing balls. Participants were asked to count bounce passes and aerial passes by the black team. Then they were asked for the two pass counts and whether they noticed anything unusual.
To remove a potential bias in the study, the researchers had to make sure the people who noticed the gorilla also were counting basketball passes; otherwise, people who weren't counting passes would be more likely to notice the distraction. So only video viewers who were at least 80 percent accurate in counting passes were analyzed.
But first, if you're one of the few who hasn't tried this before, take a look at this YouTube video. Try to count how many times the basketball players in white shirts pass the ball around.
The video, posted on YouTube in various forms for years, has registered millions of hits -- and the psychologists who devised the test, led by Daniel Simons of the University of Illinois, reported that half the people they tested were so focused on the ballplayers that they actually missed the gorilla.
In the new basketball-tossing vid, a gorilla also makes a brief appearance, but some other mildly noteworthy events also occur. Many people nowadays know that a gorilla will appear; but even though they are expecting unexpected events, those in the know are no better at clocking the non-gorilla oddities.
"You can make two competing predictions," says Simons. "Knowing about the invisible gorilla might increase your chances of noticing other unexpected events because you know that the task tests whether people spot unexpected events. You might look for other events because you know that the experimenter is up to something."
However, only 17 per cent of those who were familiar with the original gorilla video noticed one or both of the other unexpected events. Some 29 per cent of those who were unfamiliar with the original gorilla video spotted one of the other events.
This page provides links to videos from the experiment that led to their award (the "basketball" video). From here you also can visit the Visual Cognition Laboratory web site (Prof. Simons' lab) and view videos from other studies of visual awareness from Simons' research.
View the "basketball" video
This link takes you to the basketball video from an experiment by Daniel Simons and Christopher Chabris. When viewing the video, try to count the total number of times that the people wearing white pass the basketball. Do not count the passes made by the people wearing black. When you're done, visit the main lab web site for more information. Please note that this video is copyrighted and is available on this web site for viewing purposes only -- it may not be downloaded, copied, saved or used for any other purpose. If you are interested in using this video in any other context, it is available on DVD from Viscog Productions, Inc. Please see the link below. (Note that the University of Illinois is not in any way affiliated with Viscog Productions and this link does not represent an endorsement of Viscog Productions or its products by the University.)
Purchase the DVD
This link takes you the Viscog Productions web site. The site has information about the Surprising Studies of Visual Awareness Volume 1, a DVD that includes many of Prof. Simons' videos and demonstrations (including the "gorilla/basketball" video). The DVD is the only form in which any of our videos are available for use, and it is designed as a presentation tool, with menu-driven access to a variety of clips. (Note that the University of Illinois is not in any way affiliated with Viscog Productions and this link does not represent an endorsement of Viscog Productions or its products by the University.)
I can vouch for this result. I have shown this video during many ethics lectures and, nearly always, about one-half of the audience reports that they did not see the gorilla. This is a compelling way to demonstrate that sometimes we simply do not see what is right before us.
38c6e68cf9