Studies have revealed that women find those with calmer men more attractive Now, scientists have discovered why this is so.

First, the scientists recruited 39 healthy young male students from the same university and measured their cortisol and testosterone levels from saliva samples. The researchers next had 42 female students rank these men by attractiveness, masculinity, and health.

There was a false impression that they would prefer those with a higher percentage of testosterone. The hormone is related to male facial features, such as larger jaws and heavier eyebrows, and is typically associated with better long-term health.

However, previous studies have revealed that men with high testosterone levels are not automatically attractive to women, who see them as disadvantages in the long run. These macho guys may lead more unfaithful lifestyles, or they may also be bad fathers.

Instead, scientist Fhionna Moore of the University of Abertay Dundee in Scotland and her colleagues focused on the stress-linked hormone cortisol. Persistently high levels of cortisol can suppress not only the immune system, but also reproductive function. As such, it would make sense if women preferred men with low cortisol levels - that is, those who were notstressed.

Men with low cortisol levels were often rated as more attractive than men with high cortisol levels. Testosterone levels were not significantly associated with attractiveness, masculinity, or health.

The researchers also had 43 female college students view the composite images at times in and out of the fertile phases of their menstrual cycles. This allowed the scientists to see the effects that female hormones and fertility may have on perceived male desirability.

When women were in the fertile phase of their menstrual cycle (prone to becoming pregnant) - those men with low cortisol levels were seen as more attractive than men with high cortisol levels. Previous research suggests that when women are more fertile, they tend to judge men on characteristics that may best benefit them with long-term offspring, andscientists have observed that a person's overall cortisol levels are heritable.

"We speculate, then, that men with low cortisol possess something desirable that women seek to secure for their children," Moore said, "This could be, for example, good health or a healthy response to stress."

The results were considerably more complex when the women were not in the fertile phase of their menstrual cycle. In these cases, male faces with links to either high levels of cortisol and testosterone, or low levels of both hormones were rated as more attractive than faces associated with high levels of one and low levels of the other.

Previous studies suggest that when women are not in their fertile phase they tend to interpret preferences with characteristics that make a man a good long-term partner," Moore told LiveScience.

Source: LiveScience