Featured Research

from universities, journals, and other organizations

Too many sisters affect male sexuality

Date:
October 21, 2010
Source:
Association for Psychological Science
Summary:
Growing up with lots of sisters makes a man less sexy. For rats, anyway. A new study finds that the sex ratio of a male rat's family when he's growing up influences both his own sexual behavior and how female rats respond to him.

Growing up with lots of sisters makes a man less sexy. For rats, anyway. A new study published in Psychological Science, a journal of the Association for Psychological Science, finds that the sex ratio of a male rat's family when he's growing up influences both his own sexual behavior and how female rats respond to him.

David Crews, a psychobiologist at the University of Texas at Austin, is interested in how early life affects behavior later. This is an area that has received a lot of attention recently, such as research showing that the position of a fetus in the uterus matters. For example, a female fetus that spends the pregnancy sandwiched between two brothers grows up to be more masculinized, because she's been exposed to their hormones. Other researchers have found that sex ratio of the litter itself affects adult behavior. But Crews wanted to separate the effects of life before and after birth. "Life is a continuous process: you're a fetus, then you're born into a family. Each one of these periods can be important," he says -- and they don't necessarily have the same effects.

When rat pups were born, the researchers counted the number of males and females in each litter to determine the sex ratio in the womb. Then they reassembled litters in three ways: so the litters were balanced between males and females, strongly male-biased, or strongly female-biased. Then they observed the mother's behaviors toward their pups and, once the males grew up, tested them to see how they behaved with sexy female rats.

The researchers found no effects of the sex ratio in the uterus. But they did find differences in behavior based on the kind of litter in which the males grew up. When males who were raised with a lot of sisters were presented with receptive female rats, they spent less time mounting them than did male rats that were raised in male-biased litters or in balanced families. But they penetrated the female rats and ejaculated just as much as did the other males. This means "the males are more efficient at mating," Crews says.

The males may be compensating for the fact that they're less attractive to females. You can tell this by watching the females -- if they want to mate with a male, they'll do a move called a dart-hop, says Crews, and "they wiggle their ears. It drives males nuts." The females did this less when they were with a male rat that had grown up in a female-biased litter. Crews carried out the study with Cynthia B. de Medeiros, Stephanie L. Rees, Maheleth Llinas, and Alison S. Fleming of the University of Toronto at Mississauga.

These were rats, but the results have implications for humans, too, Crews says. "It tells you that families are important -- how many brothers and sisters you have, and the interaction among those individuals." Families are particularly important in shaping personalities, he says. The environment where you were raised "doesn't determine personality, but it helps to shape it."


Story Source:

The above story is based on materials provided by Association for Psychological Science. Note: Materials may be edited for content and length.


Journal Reference:

  1. David Crews, Cynthia B. de Medeiros, Stephanie L. Rees, Maheleth Llinas, and Alison S. Fleming. Distinguishing the Contributions of Prenatal and Postnatal Factors to Adult Male Sexual Behavior in the Rat. Psychological Science, (in press)

Cite This Page:

Association for Psychological Science. "Too many sisters affect male sexuality." ScienceDaily. ScienceDaily, 21 October 2010. <www.sciencedaily.com/releases/2010/10/101021113012.htm>.
Association for Psychological Science. (2010, October 21). Too many sisters affect male sexuality. ScienceDaily. Retrieved October 22, 2014 from www.sciencedaily.com/releases/2010/10/101021113012.htm
Association for Psychological Science. "Too many sisters affect male sexuality." ScienceDaily. www.sciencedaily.com/releases/2010/10/101021113012.htm (accessed October 22, 2014).

Share This



More Plants & Animals News

Wednesday, October 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Working Mother DIY: Pumpkin Pom-Pom

Working Mother DIY: Pumpkin Pom-Pom

Working Mother (Oct. 22, 2014) How to make a pumpkin pom-pom. Video provided by Working Mother
Powered by NewsLook.com
Cadaver Dogs Aid Search for More Victims of Suspected Indiana Serial Killer

Cadaver Dogs Aid Search for More Victims of Suspected Indiana Serial Killer

Reuters - US Online Video (Oct. 21, 2014) Police in Gary, Indiana are using cadaver dogs to search for more victims after a suspected serial killer confessed to killing at least seven women. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
Trick-or-Treating Banned Because of Polar Bears

Trick-or-Treating Banned Because of Polar Bears

Buzz60 (Oct. 21, 2014) Mother Nature is pulling a trick on the kids of Arviat, Canada. As Mara Montalbano (@maramontalbano) tells us, the effects of global warming caused the town to ban trick-or-treating this Halloween. Video provided by Buzz60
Powered by NewsLook.com
White Lion Cubs Unveiled to the Public

White Lion Cubs Unveiled to the Public

Reuters - Light News Video Online (Oct. 21, 2014) Visitors to Belgrade zoo meet a pair of three-week-old lion cubs for the first time. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins