In a small basement laboratory of Elliot Hall, University students stared at naked pictures on computer screens, though they didn’t know it. And it was all for science.

University psychologists discovered that when nude images are subliminally shown to people, their brains still recognize them. The study reveals new insights into unconscious brain activity.

Sheng He, a psychology professor who oversaw the study – released Monday on the Proceedings of the National Academy of Sciences Web site – said researchers used a special technique to ensure images were essentially invisible to the conscious minds of study participants.

The erotic images were masked by images “similar to snow on a TV screen,” he said.

He said the researchers were interested in determining whether invisible images affect spatial attention.

“And the answer is yes,” he said. “It’s like you’re here talking to me, so your attention is here, and someone knocks on the door and then your attention is there, but you don’t want to be rude so you keep looking at me.”

The researchers used naked photos, he said, to ensure images would clearly identify data trends, but any image that creates an emotional response would produce the same results.

He said they also learned participants’ visual attention changes based on gender and sexual orientation.

Four groups of 10 people – straight men, straight women, gay/bisexual men and gay/bisexual women – participated in the experiment.

According to the study results, straight men’s attention was attracted to a space when shown an invisible image of a naked woman and repelled from a nude male image. Similarly, straight women were attracted to pictures of naked men, but they did not react strongly one way or the other when presented images of nude women.

Gay men behaved similarly to straight women, he said. The study showed the responses of gay/bisexual women to be in between those of straight men and straight women.

Naotsugu Tsuchiya, a California Institute of Technology postdoctoral scholar, said he and his colleague Cristof Koch developed the technology used by the University researchers in their experiment.

Tsuchiya said he found the results to be very interesting because, while previous studies have already shown unconscious processing of information, they have not shown how a person’s gender and sexual orientation affected his or her reaction.

“As far as I know, their study is the first to show that a naked body of the opposite sex is processed in a different manner than that of the same sex,” Tsuchiya said. “It’s surprising that that can be done in an unconscious manner.”

Another interesting aspect of the study, he said, is that it might help explain what causes one’s sexual orientation.

“I was personally very curious about whether sexual orientation is a genetically formed thing or not,” Tsuchiya said.

Yi Jiang, a third-year psychology graduate student, said he developed and administered the experiment because he is fascinated by how images seen unconsciously can affect people’s attention and behavior.

Jiang said he is interested in developing similar experiments using invisible pictures of spiders or snakes or other images commonly associated with phobias. Such research might reveal whether or not a phobia can also modify a person’s unconscious spatial attention.