Men who find themselves in the company of fertile women are more likely to make creative attempts at sentence structure to signify their mating fitness, a study has found.

Researchers discovered that when young men talk with a woman who is in the fertile period of her menstrual cycle, they react to small changes in her facial skin tone, vocal pitch and scent. The changes activate their mating goals and cause them to shift the way they speak.

Conversational partners often align their linguistic choices to demonstrate affiliation, but when men talk to fertile women they are less likely to copy their sentence structure - and more likely to try to stand out, the researchers found.

Their study, led by Michael Kaschak, an associate professor of psychology at Florida State University in Tallahassee, is published in the journal PLoS ONE.

In one experiment, they studied 123 male college students as they took turns interacting with five female college students at different times in their menstrual cycles.

After getting to know each other, the men and women had to give one-line descriptions of a group of drawings.

When the women were at the low point of their menstrual cycle, the men mimicked their sentence constructions 62% of the time. When they were at their peak, the men did so 49.7% of the time.

The results reflected the idea that men may use “non-conforming behaviour” to stand out to potential mates, the researchers said, but was “at odds with a wide range of data suggesting that attraction to a conversational partner should lead to an increase in matching behavior”.

Dr Kaschak said that “being creative is a way of showing one’s mental acumen. Within the context of our experiment, non-aligning sentence structures may be used as a way of showing creativity or non-conformity so that you can stand out a bit.

"We’ll need to do more research to pin down the motivations more precisely - for example, is it creativity, non-conformity, or some combination of both, that is motivating the behaviour?”

Although he did not ask the men in the study if they knew what they were doing, Dr Kaschak said that “structural repetition effects are virtually always unconscious; participants have no idea that they are repeating the syntactic structures of their conversation partner. I’d bet that the same is true for the men in our studies.”

Nenagh Kemp, a lecturer in the School of Psychology at the University of Tasmania, said there was ample evidence that under normal circumstances, someone else’s choice of sentence construction can influence our own.

“If we hear someone else describe a scene as "The teacher is reading a book to the children”, we’ll be more likely to describe a subsequent scene with the same grammatical pattern, for example, saying “The farmer is giving some hay to the horses”, rather than “The farmer is giving the horses some hay”.“

The research extended current thinking about the attractiveness of non-conforming behaviour by showing how men would switch between different grammatical constructions when engaging with women.

"It seems that men can show off their potential as a partner by structuring their sentences a little bit differently, and that this propensity varies according to how receptive the woman appears.”