To test the theory, researchers at the University of Illinois put together a study in which volunteers watched a video of two groups of people — some dressed in black, others in white — passing basketballs back and forth. Study participants were told to count the passes between those dressed in white, but to ignore those dressed in black.
At one point in the video(1), a person in a gorilla suit walked into the game, faced the camera, pounded his chest, and then walked out of view.
Now, some of the study participants knew that the gorilla would appear while others weren’t expecting it. And, as it turns out, all of those who had prior knowledge of the event spotted the gorilla – while only about half of those who weren’t looking for it spotted the unexpected event.
However, just 17% of those who were expecting the “unexpected” gorilla spotted one or more other “unexpected” events in the video (such as the background curtain changing color, and one player left the scene) – only about half the number (29%) of the study participants who didn’t have foreknowledge of the gorilla – but who, apparently, were more cognizant of other unexpected events.
Interestingly, this finding was actually consistent with a phenomenon called “satisfaction of search”; where people have been found to be less likely to search for additional targets once they have found their original target.
“The main finding is that knowing that unexpected events might occur doesn’t prevent you from missing unexpected events,” researcher Daniel Simons, a psychology professor at the University of Illinois at Urbana-Champaign, said in a university news release.
In other words, when people know to look for an unexpected event, they tend to notice THAT event, but were less likely to notice the truly unexpected events. So, apparently foreknowledge of unexpected events might simply blind you to others.
The study appears in the new journal i-Perception at http://i-perception.perceptionweb.com/fulltext/i01/i0386.pdf
(1) A version of the original perception study can be see at http://www.youtube.com/watch?v=P1Q0R8rkQxE&feature=fvsr