College of LAS « Illinois

Faculty Focus

Invisible Gorillas

Why we don’t always see the gorillas in our midst.

Simons and gorilla in the background

Daniel Simons is perhaps the only university professor to ever present new research to his esteemed colleagues while dressed in a gorilla suit. Simons did it at the 2010 Illusion of the Year Contest, striding onto the stage holding a microphone and dressed like something from Planet of the Apes. He added a necktie for a touch of formality.

But there was a method to his madness. Simons, an LAS psychology professor, was introducing this group of vision scientists to a variant on what might be one of the best-known perception studies—an experiment involving a gorilla suit. He developed the original study, dubbed “Gorillas in Our Midst,” while teaching an undergraduate research methods class at Harvard in 1998. But he and the students never imagined it would become a worldwide sensation.

In the original study, participants were asked to view a video that depicted two groups of students—one group dressed in white and the other in black. They were asked to count the number of times that the white group passed a basketball among themselves. The catch is that while both teams were passing basketballs, a woman dressed in a gorilla suit wandered into the scene, stopped to thump her chest, and then strolled off-camera.

Roughly half of the participants did not see the gorilla. They were too focused on counting basketballs.

“Not seeing the gorilla is so counterintuitive that it’s jarring,” Simons says. “For the first five years or so, every single time I showed the video in a talk, I was convinced that everybody in the audience would notice the gorilla. It took years to finally understand that that wasn’t going to happen.”

The experiment has been copied in many different countries, but the result is always the same. About half of the people do not see the gorilla. According to Simons, when people are told about the gorilla and then view the video a second time, some are convinced that the tapes have been switched.

The video went viral, getting emailed from person to person. But word really began to spread in 2001 when The New Yorker mentioned the experiment; since then, it has been discussed in Newsweek and on TV programs ranging from Dateline NBC to CSI. In 2004, the illusion even earned Simons and his collaborator on the study, Christopher Chabris, an “Ig Nobel” Award, handed out annually to researchers whose experiments make people laugh and then make them think. Simons’s trophy—a pie tin with the words “2004 Ig Nobel Prize Medal” scrawled on it—sits proudly on top of his Monty Python DVDs in his office at the U of I’s Beckman Institute.

YouTube video

The gorilla experiment showed that “we’re only aware of a relatively small portion of our visual world at any moment,” Simons says. We assume we see most unexpected events in our field of vision, but we don’t realize just how much we’re missing.

As attention grew around the experiment, Simons and Chabris realized that the invisible gorilla was a metaphor for a much broader concept—that our intuitions deceive us in many ways. In their new book, The Invisible Gorilla, they describe how our intuitions deceive us in six areas—memory, perception, confidence, knowledge, cause, and potential.

For instance, they describe research showing that people have a strong tendency to exaggerate their abilities in their minds—the illusion of confidence. Simons says this explains how people, with clearly no singing ability at all, will audition for American Idol and then throw a fit when they are not chosen to move to the next round.

“In fact, the people who are the least competent often are the most overconfident about their skills,” he says. It’s called the “unskilled and unaware of it” effect.

To test this theory, Simons, Chabris, and their colleague Daniel Benjamin studied a group of highly intelligent people who have a precise measurement of their abilities—chess players. Competitive chess players are given numerical ratings based on whom they lose to and whom they beat. It doesn’t take long for these ratings to become calibrated and highly accurate. So they asked players at the World Open tournament two basic questions: “What is your current rating?” and “What should your rating be to accurately reflect your current strength?”

A little over 70 percent of the chess players said their rating should be higher—an average of 100 points higher. This is a dramatic level of overconfidence, Simons says, especially since experienced chess players should know that their ratings are extremely accurate measures of their actual skill. What’s more, the chess players who were rated in the bottom quarter had a much higher degree of overconfidence than the players in the top quarter.

One reason for overconfidence, he explains, is that when people succeed, they usually attribute it to their ability; but when they fail, they often attribute it to dumb mistakes, not inherent skill.

“We tend to keep track of cases that are consistent with our positive views of ourselves and forget the cases that are not,” he says. “It’s called the ‘self-serving bias.’”

The same illusions are in play in other areas, such as memory—even memories tied to emotional events, such as 9/11.

“We tend to mistake the vividness of our memories for accuracy,” Simons says. “When we recall something, especially something that’s emotional, we feel like we’re playing back a videotape.” The reality is that vivid memories suffer from the same distortion, forgetting, and embellishment as more run-of-the-mill memories, such as remembering people’s names.

Simons says research on memories surrounding events such as 9/11 and the Challenger explosion have shown the fallibility of emotionally charged memories and how they change dramatically with time. In The Invisible Gorilla, he and Chabris illustrate this when they discuss the infamous case in which Indiana basketball coach Bobby Knight allegedly choked a player, Neil Reed.

Reed reported that Knight choked him for about five seconds during practice before two assistant coaches had to pull Knight away. Knight, on the other hand, barely remembered the incident. He said the worst he might have done is to grab Reed and move him. Video evidence surfaced later and showed that both memories were flawed. It showed Knight grabbing Reed by the front of the neck for a few seconds and then pushing him. But no coaches separated them, as Reed maintained.

Knight’s distorted memory downplayed the event because he perceived it as nothing out of the ordinary for a normal practice, Simons says. But Reed embellished the event because to him it was a jarring and unusual event. Both men distorted their memory to make it more consistent with their “internalized, personal narrative.”

Simons continues to punch holes in our illusions, and he did so at the 2010 Illusion of the Year festivities by presenting a new take on the invisible gorilla video. People were shown what appeared to be the same old video with the gorilla wandering among players passing a basketball. But two new twists were added: One of the players wanders off-screen, and the curtain in the background slowly changes from red to gold.

When he first conducted this study on the U of I campus, all of the students who were familiar with the original video saw the gorilla, of course. But fewer than 30 percent noticed even one of the two new unexpected events.

“Once people spotted the gorilla, they stopped their search—a phenomenon known as ‘satisfaction of search,’” he says. “Once you find the obvious thing, you stop looking for other things.”

This kind of problem plagues professions like radiology, Simons says. Radiologists looking for a broken bone on an x-ray will usually stop searching once they spot what they’re looking for, often missing something else, such as a small tumor.

“It turns out that unexpected things don’t draw our attention,” he explains. “That’s the surprising thing, and it’s a consequence of something that’s good for us—focused attention. Most of the time we want to stay focused on what we’re trying to do, without being distracted by every little thing. The consequence is we sometimes filter out things we want to see. The bigger problem, though, is that we don’t realize how much we’re missing.”

By Doug Peterson
Winter 2011