Female fish - and humans? - lose interest when their male loses a slugfest

You may think of your love for your mate as the noble emotion of a pure heart, but some primitive parts of your brain are taking a decidedly more pragmatic approach to the subject, according to Stanford biologists.

In experiments with African cichlid fish, the scientists discovered that when a female shows a preference for a particular male, but then witnesses him losing a fight with another male, her feelings toward him change.

Areas of the female's brain associated with anxiety showed increased activity after witnessing an altercation.

"It is the same as if a woman were dating a boxer and saw her potential mate get the crap beat out of him really badly," said Julie Desjardins, a postdoctoral researcher in biology. "She may not consciously say to herself, 'Oh, I'm not attracted to this guy anymore because he's a loser,' but her feelings might change anyhow."

"Our intuition is that this response is likely to occur under similar conditions in humans because the brain areas involved are present in all vertebrates and perform comparable functions," said Russ Fernald, a professor of biology.

Desjardins is the first author of a paper describing the research, to be published online this week by the Proceedings of the National Academy of Sciences. Fernald and Jill Klausner, a recent honors biology graduate whose thesis was on this topic, are coauthors.

Desjardins said that with people, the subconscious change of heart would likely happen in response to a failure in any competitive situation - whether it's losing at a game or missing out on a promotion at work - not just a brawl. She said that men might also feel differently after seeing a "female of interest" fail at something competitive.

But all is not necessarily lost for the loser - at least not the human one.

All is not lost for the loser

We can take heart, she said, because we have so much more cognitive ability than fish and can reason our way out of these subtle twinges of doubt. And not all pair-bonding relationships are equal.

"Obviously, long-term committed relationships are very different than, say, people who have just started dating, or are in the initial phases of mate choice," Desjardins said. So losing a game of beer pong may - or may not - have relationship-ending consequences.

Among the fish, the researchers also found that when the preferred male prevailed, the female showed increased excitation in parts of the brain associated with reproduction, as well as some of the brain's pleasure centers.

"In this case, she is turning on her body to get ready to physically mate with this male that she previously chose," Desjardins said. The female also appears to be feeling some sort of pleasurable stimulus in her body, she said.