for the second visit, although IDs are checked and the volunteers are scrupu- lously screened. There is only one choice of beverage to order here. Each volunteer receives a dose of ethyl alco- hol according to body weight. Ten minutes later, another dose. Out comes the large beige steel box exotically named the Intoxilyzer® 5000, an infra- red evidentiary breath analyzer. Breathe into it, measure and record. In another ten minutes, administer another pre- cisely-measured dose of alcohol. Out
THE VOLUNTEERS KNOW THE DRILL. ... BREATHE, MEASURE AND RECORD YET AGAIN, UNTIL A BLOOD ALCOHOL CONTENT APPROACHING 0.1 PERCENT IS ACHIEVED BY EACH PARTICIPANT.
comes a Lifeloc FC10, unfortunately familiar to anyone ever stopped by law enforcement and asked to blow into a portable breathalyzer. The volunteers know the drill. Breathe out, measure and record. Another dose is adminis- tered. Breathe, measure and record yet again, until a blood alcohol content approaching 0.1 percent is achieved by each participant. Try following the dancing black dots across a computer screen after that. More eye movement measurements, more data, more waiting. Then it’s time to sober up. Researchers call cabs to take everyone home.
Mark Nawrot thought a research study involving 100 proof vodka and orange juice might raise a few eyebrows, particularly on a college campus. But he was focused on finding the answers to some questions. Little did he know the answers he found would appear in media around the world.
As a neuroscience researcher and associate professor in the Department of Psychology at NDSU, Nawrot stud- ies how the eyes and the brain work together. He and researchers Benita Nordenstrom and Amy Olson are
particularly intrigued by the crucial connection between eye movements and depth perception. What would happen if alcohol disrupted it?
Nawrot patiently explains the science of eye movements, with infectious enthusiasm for the subject. “Eye move- ments track in two speeds – fast, called saccadic, and slow, known as pursuit,” he says. “We use fast eye movements to dart our eyes and direct our attention to an object,” he says. “We use slow eye movements to fix our gaze and track moving objects.” As we read a book or a magazine article, for example, we use fast eye movements as our eyes jump from point-to-point, following each line of text. A basic understanding of eye movements is one step to under- standing the perception of depth, which relies on the slow eye movement system.
Try remembering the first time you parallel parked a car or made a left turn without a green-arrow light in rush-hour traffic. Judging your spatial relationship to other objects can result in successful driving or in a fender bender. It is the practical application of one type of depth perception known as motion parallax-depth perception caused by our own motion.
When going about our daily rou- tines, the visual perception of depth is usually quick and effortless. We judge it almost automatically, or at least our brain interprets it through our eyes. Whether walking or driving, we con- stantly use motion parallax to judge what’s nearer or farther. What’s our spatial relationship to the door or the tree or that car?
The messages received from our eyes and processed at lightning-fast speeds by our brain allow us to move about without running into things. What’s going on in our brain as we unknow- ingly calculate this depth? And what is the impact of alcohol on our ability to do it?