People often turn away from violence, but even those who can bear to look may not see the whole picture, according to new findings by University psychologists in collaboration with a Vanderbilt professor.

Exposure to violent images can prove so powerful that it can elicit temporary functional blindness, the study by Steven Most, a psychology postdoctoral fellow, psychology professor Marvin Chun and their former colleague, Vanderbilt psychologist David Zald, found. The results of the two studies performed on Yale undergraduates, published in the August edition of Psychonomic Bulletin and Review, report that images can induce a spontaneous “attentional blink” that can last anywhere from one-fifth to half a second.

Most said he expected subjects to have a short deficit in visual processing after viewing an emotional image, but several aspects of the results relating to individual personality differences proved surprising.

“We did predict that there would be individual differences as a function of a person’s personality, but we found no systematic differences. Everyone showed the effect,” he said.

The findings have significant real-world applications in a number of different areas, Zald said. Advertising and billboards with emotional images could present a risk to pedestrians when a driver is blinded for a brief period, he said. The reliability of some eyewitness testimony, he said, could be also be called into question, as a person viewing a violent image will likely miss details of the scene. The findings could affect military training, Zald said. Soldiers likely to encounter gory situations could benefit from specialized training so they can cope with the blindness brought on by combat, he said.

“If a soldier is out there and sees someone getting shot or blown up, they are likely to have same sort of temporary blindness and not being able to see what’s going in their environment,” Zald said.

Personality differences manifested themselves to some degree when the experiments manipulated the amount of information provided to the participants about the image, Most said. More anxious participants were less able to overcome their biases and exhibited blindness, while less anxious individuals were better able to override their biases and largely overcame the effect, he said.

Most of the pictures used in the experiment came from a group of images rated by the degree of pleasure and arousal they produce, Zald said. The studies focused specifically on unpleasant situations that “unless someone is a surgeon, are very graphic,” he said. The length of the lapse produced by an emotional, unpleasant image interspersed with neutral images varied among the participants, a phenomenon likely attributable to personality differences, Zald said.

Functional blindness has been studied previously, but the recent findings introduce a new element into research on the concept, Chun said.

“The additional twist is we figured that emotional stimuli would capture attention and might make people functionally blind to other things in the scene,” Chun said.

Separate follow-up studies substituting erotic images for violent images but utilizing the same method have not yet been published.