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You can't focus on everything at once. Here's why

No, you really can't focus on the road while you're yakking away on your cell phone -- and a new study explains why.

This new research builds on the well-known "Gorillas in Our Midst" experiment, a staple of Psych 101 courses. Researchers say they can now explain why many people fail to see a "gorilla" who unexpectedly appears in a video when their attention is focused on another task -- it's because they have lower "working memory capacity," a measure of the ability to keep your brain tuned into many things at once.

In the study, 197 psychology students (ages 18 to 35) watched a 24-second video of six people playing basketball. They were asked to count the number of bounce passes and aerial passes made by the black-shirted team. Twelve seconds into the video, an actor dressed in a gorilla suit walks into the hoops game, pounds his chest, then leaves. The "gorilla" appears on screen for eight seconds.

After viewing the segment, researchers asked participants for the two different pass counts and whether they noticed anything unusual in the clip. Slightly more than half the participants, or 58 percent, noticed the ape but 42 percent did not.

Why the gorilla is 'invisible'

Scientists have wondered why roughly half the people who watch this video see the hairy beast while others completely miss it. Psychologists call this effect "inattentional blindness." It's an inability to see something, typically an unexpected object, when your attention is wrapped up in something else.

"Tasks that require a lot of attention, concentration or mental effort could be more likely to raise the risk of inattentional blindness," says Janelle Seegmiller, a doctoral student in psychology at the University of Utah in Salt Lake City and the study's lead author. (This research will appear in the May issue of the Journal of Experimental Psychology: Learning, Memory and Cognition.)

The gorilla study "demonstrates that people are more likely to miss unexpected events that are in their visual field when they are cognitively stressed as well showing that people with lower working memory capacity may also be more susceptible to missing them," she points out.

While completing difficult tasks, people with higher working memory capacity can keep more information in their minds. And these folks are more likely to see the gorilla. That's because they "have more attentional resources allowing them to use any 'leftover' resources to monitor the environment and notice the gorilla," explains Seegmiller.

In fact, researchers found that among participants who were most accurate in counting basketball passes in the video -- the original task at hand -- 67 percent of those with "high working memory capacity" observed the gorilla but only 36 percent with "low working memory capacity" did.

Although psychologists currently believe that your working memory capacity is not something that can be trained or dramatically changed, you're not doomed to miss things right before your eyes if yours is low. The trick is to have "leftover" attention so you notice the unexpected.

Not glimpsing a gorilla in a lab video is one thing, but imagine what you could be missing out on in real life. "We could find similar results with driving and unexpected events (like a car in front of you quickly breaking)," says Seegmiller. Or people having cell phone conversations while behind the wheel -- then sailing through a stop sign. Or looking but not seeing another vehicle and causing a fender-bender.

Missing the gorilla is a problem of processing information and focusing a hard-working brain. It's helpful to filter out information that's irrelevant to a task, which helps you pay attention to what's important. But this can also be harmful when something unanticipated isn't noticed and should have been.

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