She thinks friends, he thinks sex

Imagine the following scenario: a woman and a man are having a conversation. She is interested in the conversation, and is friendly, smiling and warm. He interprets her behaviour as sexual interest.

Or maybe: a man is sexually attracted to a woman he has just met, and signals this in various ways. She thinks that he is just being friendly.

Recognize these situations? If so, you're not alone.

We misunderstand each other

In a recent study at the Department of Psychology at NTNU, women reported that men often misinterpret their signals of friendliness as sexual interest. Conversely, the men in the study reported that women often misinterpret their signals of sexual interest as friendliness.

"The results are no surprise, seen from an evolutionary perspective," researcher Mons Bendixen explains. "The fascinating thing is that our results are identical to a study done in the USA, even though Norway is one of the most gender-equal, sexually liberal countries in the world."

In most areas of psychology, there is little to no difference between genders: mental capacity, intellectual achievements, food preferences -- men and women are all more or less the same. But when it comes to reproduction and challenges related to finding a sexual partner, there are suddenly differences to be found.

Evolutionary psychology is the study of how the human mind has evolved, developed and adapted over time. One thing that evolutionary psychologists are specifically interested in is gendered sexual psychology between cultures and social groups. Seen through the lens of evolutionary psychology, we can better understand why men often wrongly assume that women who smile and laugh during conversation may want to sleep with them.

Men can't be picky

A man's ability to reproduce is all about seizing every opportunity. He has to spend both money and time on courtship, which still may not lead to sex. But it costs even more to not try, because then he won't be able to reproduce.

"A man's reproductive fitness, meaning the amount offspring he produces, is dependent on how many women he is able to make pregnant. But that's not how it works for women," Bendixen explains.

A woman can have sex with multiple men over a short period of time without producing any more children. So for men, it is a low-risk, potentially high-reward situation for men to have sex with women whenever the opportunity presents itself.

On the other hand, the cost is potentially great for a woman if she thinks that a man is more sexually interested than she is. A woman risks pregnancy, birth, nursing and raising the child, as well as lost oppotunities to reproduce with others. Across thousands of generations, women's psychology has evolved to set the bar higher, which means they need much clearer signals than men before they consider sex.

"Even though these processes aren't conscious, we can still empirically measure the results," Bendixen says.

Similar to an American study

The recent study at NTNU included 308 heterosexual participants between the ages of 18 and 30. Fifty-nine per cent of participants were women.

The participants were all heterosexual because sexual intercourse between men and women is necessary for reproduction. Half of the women and 40 per cent of the men were in relationships. The questions were identical to questions asked in a similar American study from 2003. Here are a few examples:

Have you ever been friendly to a person of the opposite gender, and had your actions interpreted as sexual interest? If yes, how many times has this happened?

Have you ever been sexually attracted to someone and shown interest, and had the other person misinterpret your signals as friendliness? If yes, how many times has this happened?

Men misinterpret most often

The results show that both men and women find that their social signals are misinterpreted by the opposite sex. Women in the study answered that they had acted friendly towards a man about 3.5 times over the past year on average, and had this misinterpreted as sexual interest. The men in the study also reported having been misinterpreted by the opposite sex in this way, but far less often.

The results also show that men rarely misinterpret women who actually do signal sexual interest. The study also shows that this is independent of whether or not the person is in a steady relationship or not.

Bedixen points out that Norway is considered to be one of the most gender-equal countries in the world. The USA, on the other hand, where a similar study was done in 2003, is ranked as 20th on the World Economic Forum's list for equality around the world. "The fact that the hypothesis in evolutionary psychology is supported even when the study is in a society where gender equality is strong, weakens alternative claims that the social roles of men and women in different cultures determine their psychology in these situations," he says.

Does not excuse sexual harassment

Researchers at the Department of Psychology are now going to use data collected from high school students to see if the results of this study are also valid for people aged 16-19, and if these miscommunications might lead to sexual harassment.

"Even though evolutionary psychology and our findings can help account for some sexually inappropriate behaviour in men, it doesn't mean that evolutionary psychologists defend this happening. Measures can be taken to prevent sexual harassment. It will help if we just teach men that a woman who laughs at your jokes, stands close, or touches your arm at a party doesn't mean that she's sexually interested, even if you think she is," Bendixen says.