Women, according to new research, are seeking intellectual, shy, calm, methodical men — for sperm donors, that is. A study from QUT Queensland’s Behavioral Economics Group examined the kinds of men women choose as sperm donors and found that certain, somewhat unexpected, personality traits were indicative of a donor women were most likely to select.

Worldwide demand for sperm donors has been increasing recently, so an informal online market has emerged. More and more offspring are being produced outside of formal fertility settings, according to Stephen Whyte, co-author of the study. He explained that the results of the research were not what he and co-author Professor Benno Torgler had anticipated.

“You would expect in an informal online setting, men would have to sell or promote themselves to women, and extroverted men should be better at doing that,” Whyte said in a press release. “But what we find is actually the opposite.”

In what the authors believe is the first study to look at males who are donating through unregulated forums, the study dealt with data from 56 men.

“This online donor market works quite differently to fertility clinics in that it facilitates more interaction between the recipient and the donor,” Whyte said. “This allows us to explore individual donor personality characteristics and how likely they are to be chosen by women as their donor.”

The data showed that women were much less likely to choose the sperm of socially awkward or fretful men, but the same was found for lively, extroverted personalities. It appeared that a middle ground existed, and that was the sweet spot for donor selection.

“Research has previously shown that humans are good at judging personality traits as well as levels of intelligence with only minimal exposure to appearance and behaviors, and our findings certainly seem to support that,” Whyte said.

The participants for the study were between the ages of 23 and 66, and were from Canada, the UK, Italy, Sweden, Australia, and the USA. Data was collected through online surveys on online sperm donation forums and websites.

The research also noted that 73 percent of the participants who had children by donation kept in touch with their donor children through email, phone, video, or even in person.

Source: Whyte S, Torgler B. Determinants of online sperm donor success: how women choose. Applied Economic Letters. 2015.