Interestingly, men seen in their underwear are viewed as human beings, according to the study, published in the journal Psychological Science.
This reaction, called sexual objectification, has been well studied, but most of the research is about looking at the effects of this objectification, the researchers said.
The latest study gets a grip on what humans actually do objectify -- and finds that both men and women view images of sexy women's (but not men's) bodies as objects, they said.
"What's unclear is, we don't actually know whether people at a basic level recognise sexualised females or sexualised males as objects," said study researcher Philippe Bernard of the University libre de Bruxelles in Belgium.
"What is motivating this study is to understand to what extent people are perceiving these [images] as human or not," Bernard was quoted as saying by LiveScience.
Past research has worked out that our brains see people and objects in different ways. While we're good at recognising a whole face, just part of a face is a bit baffling. Similarly recognising part of a chair is just as easy as recognising a whole chair. It's also known that recognising pictures of humans upside down is very difficult, but that is not the case with objects.
Keeping that in mind, Bernard and his team used a test in which they showed study participants images of scantily clad men and women in sexualised poses on a screen. Some of the pictures were right side up and some were upside down.
After each picture, there was a second of black screen, and then the participants were shown two images of which they had to choose one that matched the image they had just seen.
It was found that participants recognised right-side-up men better than upside-down men, suggesting that they were seeing the sexualised men as people.
But the women in their underwear weren't any harder to recognise when they were upside down -- which is consistent with the idea that people see sexy women as objects. There was no difference between male and female participants.
The findings suggest that we think of the sexy women seen in ads every day as if they were objects, not people, Bernard said. The next step is to study how seeing all these images influences how people treat real women, he said.