MONDAY, July 12 (HealthDay News) -- People who actually expect an unexpected event aren't more likely to spot these events than people who aren't anticipating anything, a new study suggests.

In the study, volunteers watched a video of two groups of people -- some dressed in black, others in white -- passing basketballs back and forth. The participants were told to count the passes between those dressed in white while ignoring those dressed in black.

At one point in the video, a person in a gorilla suit walked into the game, faced the camera, pounded his chest, and then walked out of view.

Some of the participants knew the gorilla would appear while others didn't know. All of those who had prior knowledge spotted the gorilla, compared to about half of those who weren't in the know.

However, only 17 percent of those who knew about the gorilla beforehand spotted one or more other unexpected events in the video, such as the background curtain changing color, compared with 29 percent of participants who didn't know about the gorilla beforehand.

"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.

The study appears in the new journal i-Perception.

More information

There's more on how the mind works from Harvard University.