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October 17, 2006
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Driving While Distracted (06.29.04) - While many of us are behind the wheel this July 4th weekend, we may be tempted to make a call from our cell phones. But some researchers are looking at the dangers of driving while distracted.

Brain Limits (05.20.04) - Scientists studying our brains may have found why mistakes can happen when we try to do too many things at one time. And they have found we need a little time to process everything we do.

Driving Blind (03.13.03) - Talking on a cell phone while driving can lead to fatal accidents. Lawmakers in many states are considering making it illegal to use a cell phone while driving unless you have a hands-free phone. But researchers say hands-free phones may not be safer after all.

  Attentional Blink Experiment

University of Illinois Visual Cognition Lab Demo Page

  Blinded Brains
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When we pass by something gory or racy, we often can't keep from looking.

As this ScienCentral News video reports, researchers say that affects our brain in ways that could be dangerous in certain situations.

Driving Blind

We all know the site of a tragic accident. A four by four tossed over a highway barrier. A white sheet on the ground. Police with heads bent. As we pass, it seems like the most courteous action would be to avert our eyes, but still we glance over at the awful scene.

Vanderbilt University psychologist David Zald says that's dangerous because, what he calls "emotional" images -- like car accidents, a gruesome murder scene, or a bit of pornography -- can briefly blind us to everything else around us, limiting our senses and potentially putting us at risk.

"When [visual] information comes into the brain it has to get funneled through a relatively small area… only so much information can pass though at a time," explains Zald. "So what happens is, if there's a piece of emotional information, it basically gets jammed into the space… and nothing else is passing through."

Zald and a group of colleagues based at Yale University report in the November issue of Psychonomic Bulletin and Review that they trained 21 people to spot a target image among a series of pictures flying by on a computer screen at a rate of 10 pictures per second. The target image is what the researchers call a "neutral" image, such as a picture of a building or a landscape. Study participants had to determine if the target image was rotated to the left or the right.

"Neutral images" rotated to the left and to the right.
image: David Zald
"Though the images go by very quickly, once people have a few practice trials, they can do this very well, usually about 90 percent or better," says Zald.

When the researchers displayed either a gory or an erotic image just before the target image, the participants usually missed the target image completely. Over the course of several trials, they adjusted the placement of the graphic image before the target image. The shorter the amount of time between the graphic image and the following target image, the less likely the participants were to see the target image.

Although it's only for a very brief period of time, ranging between a hundredth and a tenth of a second, Zald says emotionally charged images and scenes can "leave us temporarily blind for new incoming information."

The finding suggests that even when people are completely focused on a particular task – in the case of the study, identifying the target image – their attention is still captured by more graphic images.

In our everyday lives, it could also mean that our eyes - and therefore our attention - stray uncontrollably. Zald says that is both good and bad. In an interview, he used the example of how this phenomenon plays a role in personal safety. If someone is suddenly shot on the street, witnesses will stop reading their newspapers, take cover, and stare at the victim as he or she falls to the ground. But witnesses may not be able to transfer their attention quickly enough to also determine if the shooter is targeting them next. "The problem is that there's also a cost to it," says Zald, "Which is that we don't tend to other information when we see something that's emotional."

Illinois University psychologist Daniel J. Simons says the study is "a really neat finding," because it documents how we may be distracted by things beyond our focused attention. He adds however, that whether seeing a car accident, or a racy billboard on the road causes this blindness, has yet to be confirmed. "We don't know if it has that [specific] consequence yet."

David Zald
In order to conclusively document what happens when we're driving, Simons says researchers would need to design studies that use driving simulators to test peoples' on-the-road reactions to graphic stimuli. His own research however has shown that people often fail to see things even with their eyes wide open. "Looking out the window," he warns, "Doesn't guarantee that you will see [everything in front of you]."

Zald's team also found that some people are more easily distracted than others. "[People who] have the lowest amounts of anxiety are sort of able to override this distraction," says study co-author and Yale University psychologist Steven Most. But the research team has not yet found any other trends.

New York University psychologist Elizabeth Phelps also agrees that under certain circumstances some people may be able to suppress this emotionally induced blindness. For example, she says doctors who regularly deal with bloody injuries or people who work in the pornography industry may have become desensitized to graphic images because they are exposed to them on a regular basis. However, she says that in these situations, these professionals are not facing any immediate danger themselves. "With no consequence, is that going to extinguish their emotional response?" Phelps asks, "I think so." In other less professional and more everyday settings, she says almost everyone is susceptible to these lapses in attention.

Zald, Most and their colleagues are planning additional studies to see what is happening in the brain when this emotional blindness occurs. In the mean time, Zald reminds us all that life really can get pretty far down the road in an instant. "If something captures your attention, you may actually travel a fair amount of distance before you can actually refocus back on the road again, before you can detect something else on the road… a child that's suddenly stepped out onto the street."

This research appears in the November issue of Psychonomic Bulletin and Review and was funded by the National Institutes of Health.

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