[Paleopsych] NS: Erotic images can turn you blind

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Erotic images can turn you blind
http://www.newscientist.com/article.ns?id==dn7845
18:09 12 August 2005
Gaia Vince

Researchers have finally found evidence for what good Catholic boys have known 
all along ? erotic images make you go blind. The effect is temporary and lasts 
just a moment, but the research has added to road-safety campaigners' calls to 
ban sexy billboard-advertising near busy roads, in the hope of preventing 
accidents.

The new study by US psychologists found that people shown erotic or gory images 
frequently fail to process images they see immediately afterwards. And the 
researchers say some personality types appear to be affected more than others 
by the phenomenon, known as "emotion- induced blindness".

David Zald, from Vanderbilt University in Nashville, Tennessee, and Marvin Chun 
and colleagues from Yale University in Connecticut, showed hundreds of images 
to volunteers and asked them to pick a specific image from the rapid sequence. 
Most of the images were landscape or architectural scenes, but the 
psychologists included a few emotionally charged images, portraying violent or 
sexually provocative scenes.

The closer these emotionally charged images occurred prior to the target image, 
the more frequently people failed to spot the target image, the researchers 
found.

"We observed that people failed to detect visual images that appeared one-fifth 
of a second after emotional images, whereas they can detect those images with 
little problem after neutral images," Zald says.

Primitive brain

"We think there is essentially a bottleneck for information processing and if a 
certain type of stimulus captures attention, it can jam up the bottleneck so 
subsequent information can't get through," Zald explains. "It appears to happen 
involuntarily. The stimulus captures attention and once allocated to that 
particular stimulus, no other stimuli can get through" for several tenths of a 
second.

He believes that a primitive part of the brain, known as the
amygdala, may play a part. That region is involved in evaluating
sensory input according to its emotional relevance and has an
autonomic role, influencing heart rate and sweating.

"It is possible that emotionally-charged stimuli produce
preferential rapid routing of the impulse that bypasses the slower
cortical route via the amygdala," Zald told New Scientist. "Patients
with amygdala lesions pick out the target image without reacting to
violent images, although they show normal blindness reactions when
sexual images are introduced, which suggests another mechanism may
also be involved."

Harm avoiders

The researchers think emotion-induced blindness could lead to
drivers simply not seeing another car or pedestrian if they have
just witnessed an emotionally charged scene, such as an accident or
sexually explicit billboard.

The effect could exacerbate the more obvious problem of drivers
simply being distracted by large, arresting images. "It's the
responsibility of drivers to ensure that when they are behind the
wheel they keep their eyes on the job in hand," says a spokeswoman
from Brake, a UK road safety organisation.

And some people are more vulnerable than others. The study assessed
participants using a personality questionnaire, rating them
according to their level of "harm avoidance". Those scoring highly
were more fearful, careful and cautious; those scoring low were more
carefree and more comfortable in difficult or dangerous situations.

The researchers found that those with low harm avoidance scores were
better able to stay focused on a target image than those with high
harm avoidance scores.

"People who are more harm avoidant may not be detecting negative
stimuli more than other people, but they have a greater difficulty
suppressing that information," Zald suggests.

The Brake spokeswoman says companies should think about the
consequences of placing emotionally charged billboards at dangerous
road junctions: "We should be concerned if drivers are experiencing
split-second breaks in concentration, which could result in an
accident or death on the roads."

Journal reference: Psychonomic Bulletin and Review (August 2005
issue)