In the guppy yard, the unusual male wins

When it comes to choosing a partner, guppies often look for partners with the brightest and most interesting color patterns.

But why? It turns out that everything is a question of psychology.

In a new study, researchers at Florida State University found that these tiny tropical fish often chose a partner who physically stood out from the rest of the pack because of a common type of learning called habituation. By habit, animals – in this case guppies – stop responding to a stimulus after prolonged exposure.

In other words, the female guppy is often immune to the charms of a male guppy that looks like any other guppy. Those who have unusual colors are more likely to succeed in seducing a partner.

"If they've ever seen some models in the past, they've gotten used to them," said Mitchel Daniel, a postdoctoral researcher working with life science professor Kimberly Hughes. "But when a guppy arrives with a new pattern, he's not used to it, so he finds it more appealing.We have shown that this attraction to the unusual happens because of the addiction which means that females disagree with repetitive information, and pay more attention to things that are different. "

Their study is published in Acts of the Royal Society B.

The team's research is based on a study that Hughes conducted several years ago, which revealed that the guppies' color patterns seemed to influence the choice of the partner. When Daniel came to work in Hughes' lab, he wanted to explore the psychological theory of addiction and find out if that explained how the guppies chose their partner.

"It's hard to understand," said Hughes. "Why do women have this preference? It's a difficult problem to solve."

The researchers exposed the guppies to a large number of men with the same color patterns and followed their reactions to men 's courtship displays. In the guppy's courtship, the male guppy performs a kind of dance around the woman to express her interest. If the woman wants to participate in this nuptial parade ritual, she will react to the approach and head to the male.

The researchers then exposed the same guppies to male guppies with very different color patterns to study the response. In some cases, they isolated the group of women guppies for a short time.

The researchers found that women generally preferred new male guppies. But, they also found that male guppies with familiar patterns became interesting again for guppies kept in isolation.

Through these experiments, researchers have shown that this choice meets four criteria indicating habituation.

• First, the reactivity of guppies to a stimulus – male guppies with a familiar pattern – decreased with increased exposure.
• Second, the interest of women for men with new models was not affected by exposure to the familiar model, showing something called stimulus specificity.
• Third, they have demonstrated what is called spontaneous recovery, that is, these same women once again became interested in the familiar pattern after it was removed for a period of time.
• And fourth, they once again became interested in the initial group of guppies after being exposed to new patterned guppies, a phenomenon known as dishabituation.

"Nobody associated this idea of ​​addiction with the partner's choice for novelty," Hughes said. "This is a good example of how ideas from different fields can be helpful in explaining biology."