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Guppies with bigger brains prefer more attractive mates

It’s a guppy beauty contest

Pinke via Flickr

Here’s another advantage of having a big brain: you know how to choose the hottest mates. As it turns out, female guppies with bigger brains are smart enough to prefer attractive male guppies. Their smaller-brain compatriots weren’t as picky — which, evolutionarily speaking, is really their loss.

Choosing a mate is tricky; just think of how many considerations go into the choice. (At the very least, you have to be able to remember the two potential mates you’re comparing.) We know that big brains often correlate with better cognitive ability, and that being attractive usually gives you other advantages. So, it follows that scientists might wonder if bigger-brained guppies really do have the right preferences. In a delightful study published today in the journal Science Advances, researchers hosted what was essentially a male guppy beauty contest to test it out. And, yes, the larger-brained guppies did make the smarter choice.

In the guppy world, at least, being more colorful usually means you’d be a better mate. Colorful males tend to have bigger tails, too, which can make them better swimmers.

First, the scientists got a bunch of big-brained and small-brained female guppies. There were 36 of each, and also 16 guppies of average size just to check. (They’d all been bred to have different brain sizes, with an average of a 10 percent difference between large and small.) Next, they collected 58 male guppies and analyzed their markings. From these, they chose the eight that were most colorful and the eight that were unattractive, which the researchers described as “dull-colored with small tails.” (Sorry.)

Now, time for the experiment itself. The scientists put an attractive male in a tank next to the female’s tank and let her observe him for 15 minutes. Afterward, she saw an unattractive one.

Every trial was broadcasted live using a webcam, and viewed from a laptop, and the scientists determined preference based on how close the female guppy got to the tank with the male guppy in it. The female guppies with both large- and average-sized brains were more intrigued by the colorful males. The smaller-brained ones, not so much.

The authors sure did do due diligence: they even studied the female guppies’ eyes to make sure the results weren’t just because larger-brained guppies see color differently. Color perception doesn’t explain the preferences, after all, so they conclude that it really is that smarter guppies choose more wisely.