Researchers are saying that the perception of nude bodies is boosted at an early stage of visual processing. 

So it may be an overlap with the culturally forbidden nature of scantily clad or nude figures as the driving force behind its appeal in areas as diverse as sexual arousal, art and advertising.  Brain imaging studies have localized areas in the brain which are specialized in detecting human bodies in the environment, but it was unknown whether the brain processes nude and clothed bodies in different ways. 

Researchers at the University of Tampere and the Aalto University, Finland, have now shown that the perception of nude bodies is boosted at an early stage of visual processing.

In a study, participants were shown pictures of men and women in which the models wore either normal everyday clothes or swimsuits, or were nude. At the same time, visual brain responses were recorded from the participants' electrical brain activity, which allowed researchers to investigate and make some correlations about the early stages of visual information processing. 

The results showed that, in less than 0.2 seconds, the brain processes pictures of nude bodies more efficiently than pictures of clothed bodies - the less clothing the models in the pictures were wearing, the more enhanced was the information processing: the brain responses were the strongest when the participants looked at pictures of nude bodies, the second strongest to bodies in swimsuits, and the weakest to fully clothed bodies.

Male participants' brain responses were stronger to nude female than to nude male bodies, whereas the female participants' brain responses were not affected by the sex of the bodies. 

The results show that the brain boosts the processing of sexually arousing signals. In addition to the brain responses, the participants' self-evaluations and measurements reflecting the activation of the autonomic nervous system were in line with expectations, showing that nude pictures were more arousing than the other types of pictures.

Such fast processing of sexual signals may play a role in reproduction, and it ensures efficient perception of potential mating partners in the environment.