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BACKGROUND: New psychological findings from researchers at Vanderbilt University and Yale University show that when people are shown violent or erotic images, they frequently fail to understand, recognize and remember what they see immediately afterwards. They also found that people who are less anxious are more successful in training themselves to focus on the search for a specific image, rather than blanking out when an emotionally intense image appears.

ABOUT THE STUDY: There were two separate experiments. In the first, subjects were shown hundreds of pictures, a random mix of disturbing images and neutral landscape images. They were instructed to look for a particular target image. Two to eight pictures would flash by, and one of them was an irrelevant, emotionally negative, or neutral image. The result: the closer the negative pictures were to the target image, the more frequently the subject failed to spot the target. The second study was similar, substituting erotic images for emotionally negative ones, revealing the same basic effect.

ATTENTIONAL RUBBERNECKING: This involuntary effect ý dubbed "attentional rubbernecking" or "emotion-induced blindness" -- could be critical during witness testimony in a trial; disturbing or emotionally intense images might prevent a witness from observing all the details. It could have an impact when driving at 60 MPH, or when someone steps out into the street at the wrong time. This is not simply a momentary lapse in focus or concentration. People literally fail to see important visual elements one-fifth of a second after seeing violent or erotic images, without being aware that they have blanked out for a split second.

WHY IT HAPPENS: Vanderbilt psychologist David Zald believes there is a kind of bottleneck for information processing in the brain. If a certain type of powerful stimulus -- such as violent or erotic imagery -- captures out attention, it can "jam up" the bottleneck so subsequent information can't get through. Zald cites prior studies that demonstrated there are limits to how much information people can hold in their visual short-term memory. So we can miss something right in front of our eyes if we're paying attention to something else.

The Human Factors and Ergonomics Society contributed to the information contained in the TV portion of this report.

Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.