According to a new study, having even one stiff drink can make you literally “blind drunk” — unable to see something right in front of you.

Seema Clifasefi, a psychologist at the University of Washington, did the experiment thusly: She took a bunch of subjects and gave ‘em a highball. In some cases, the drink was actually alcoholic; in other cases it tasted like the real thing but was dealcoholized, and the subjects didn’t know which they’d gotten. Then they had to watch a 25-second clip of three people playing basketball and were asked to count the ball passes. Part way through the clip, a guy in a gorilla suit walked across the court, beat his chest, and walked off.

Here’s the thing: The people who had the alcoholic drink were twice as likely as the others to not notice the gorilla — even though it walked literally between the basketball players.

The upshot? Bad news for people who think they can have one drink and still drive competently — since obviously they won’t be able to pay attention to multiple stimuli. As Clifasefi said in a press release:

“We rely on our ability to perceive a multitude of information when we drive (speed limit, road signs, other cars, etc.) If even a mild dose of alcohol compromises our ability to take in some of this information, in other words, limits our attention span, then it seems likely that our driving ability may also be compromised … If you’ve had one drink, you may be so focused on paying attention to your speed so as not to get pulled over, that you completely miss seeing the pedestrian that walks directly in front of your car.”

In psychological lingo, this is a test that proves “inattentional blindness” — the point at which our attention becomes so overloaded that we fail to notice things under our noses. The gorilla-suit test was invented a few years ago and has become a classic: It even works on totally sober people, since many of them, too, become so absorbed in the basketball game they fail to notice the dude in an ape suit. But nobody had ever tested whether alcohol exacerbates inattentional blindness. Now we know!

And of course, alcohol isn’t the only thing degrading drivers’ attention-spans. A flurry of recent research has shown that everything from sexy pictures to mobile phones can so impair people’s driving and perceptual abilities as to render them effectively legally blind and legally drunk. With all the Motorola Razrs glued to people’s cheeks as they cruise past enormous roadside Hooters billboards, it’s amazing the highways aren’t a towering pile of twisted, burning metal.