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February 9, 2010
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Brain Blindness


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  Attentional Blink Experiment

University of Illinois Visual Cognition Lab Demo Page



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We all know that seeing something emotional can distract us, but researchers say that it might even blind us... not in our eyes, but in our brains. This ScienCentral news video explains.

Driving Blind

It's hard not to look when you pass an accident on the road, but doing so can be dangerous. Vanderbilt University psychologist David Zald says "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.

"Something that's emotional not only captures our attention, but it does it to such an extent that it's blocking information that comes in after. We're no longer even looking at that image," says Zald.

As reported in Psychonomic Bulletin and Review, Zald and his colleagues trained twenty-one people to spot a neutral target image out of a series flying by at ten pictures per second, and then state whether it was rotated to the left or the right. The volunteers performed well except when either a gory or erotic image — more graphic than can be shown here — appeared before the target image. Co-author Steven Most, from Yale University, says in those cases participants were far more likely to miss the target.





test images
"Neutral images" rotated to the left and to the right.
image: David Zald
"When an emotional picture appears, it seems to short-circuit that processing in the brain that will then help you construct a visual conscious perception," Most explains.

Zald says these emotional blindings happen all the time in our daily lives, but are probably most important for drivers, since a lapse in attention of less than a second is enough to cause an accident.





"A ball that's suddenly come out on the road, a child who's suddenly stepped into the street… Anything that could happen very quickly, we could easily miss it," says Zald.

In a separate interview, Zald gave an 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."




The research 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," Most says. But they have not yet found any other trends.

David Zald
David Zald
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."

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]."

Elizabeth Phelps, a psychologist at New York University, 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.

This work was reported in the November 2005 issue of Psychonomic Bulletin and Review and was funded by the National Institutes of Health.


 
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