'Ape-earances' can be deceiving for many under the influence of alcohol

June 30, 2006

It's pretty difficult to overlook the proverbial 800-pound gorilla, or even an average-size person dressed in a gorilla suit. But a new study indicates that people who were given a simple visual task while mildly intoxicated were twice as likely to have missed seeing the person in a gorilla suit than were people who were not under the influence of alcohol.

The study, appearing in the current issue of the Journal of Applied Cognitive Psychology, is the first to show visual errors caused by "inattentional blindness" are more likely to occur under the influence of alcohol. This phenomenon occurs when important, but unexpected, objects appear in the visual field but are not detected when people are focused on another task, according to Seema Clifasefi, a postdoctoral psychology researcher at the University of Washington.

While the research, a pilot study, did not test driving aptitude, the study has strong implications for people operating motor vehicles after consuming alcohol, according to Clifasefi, who is affiliated with the UW's Addictive Behaviors Research Center.

"Driving requires our full attention. We need to perceive information from a variety of sources when we are driving, but alcohol reduces our ability to multi-task. So we focus on one thing at the expense of everything else," she said.

"Say you have been at a party and are driving home after having a couple of drinks. You don't want to be stopped for speeding, so you keep eyeing the speedometer. Our research shows that you will miss other things going on around you, perhaps even a pedestrian trying to cross the street."

In the study, 46 adults ranging in age from 21 to 35 were brought into a bar-like setting. Half of them were given drinks containing alcohol to bring their blood alcohol level up to 0.04 -- half the legal level for being drunk in most states. The other half were given drinks containing no liquor.

After the volunteers had their blood alcohol levels measured by a breath test, they were taken to a computer monitor and asked to watch a 25-second film clip. The clip showed people playing with a ball and the volunteers were told to count the number of times the ball was passed from one person to another. In the middle of the clip a person dressed in a gorilla suit appeared, walked among the players, beat its chest and then walked away.

Afterward, the subjects were asked if they saw the gorilla. Just 18 percent of the drinkers said they noticed the gorilla while 46 percent of the sober subjects indicated they saw the gorilla.

In the future, Clifasefi hopes to do a larger study testing inattentional blindness using a driving simulator.

The National Institute of Alcohol Abuse and Alcoholism funded the research. Co-authors of the study are Melanie Takarangi, a doctoral student at Victoria University of Wellington in New Zealand and Jonah Bergman, a recent UW graduate.

Source: University of Washington