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American Association for the Advancement of Science

There's something about a face

Female Poliste fuscatus paper wasps have unique faces that are used for individual recognition.
[Image Science/AAAS]

It's easy for people to tell one human face from another. We do it all the time without even thinking about it. But, it does take a special ability.

Imagine trying to distinguish one goldfish face from another, or one squirrel face, or one wasp face. Within each of these species, all the faces look pretty much the same, right? In contrast, there's something about the human face that our brains recognize and remember in fine detail.

Not all animals recognize each other's faces like this. We know some mammals do, but other animals recognize each other by smell, for example. New research shows that paper wasps also have this special face-recognizing ability, which is interesting because wasps have dramatically different eyes and brains from mammals.

The key seems to be that, like us, paper wasps are highly social. Being able to identify each other by their faces probably benefits the wasps in the cooperative colonies they live in.

Paper wasps, which you may know from the delicate, honeycomb-like nests they build, live in colonies with multiple queens. The offspring of each queen work together.

Michael Sheehan and Elizabeth Tibbetts of the University of Michigan hypothesized that the paper wasps, also called Polistes fuscatus, would be able to learn to identify images of faces faster and more accurately than other types of images.

The researchers trained the wasps to tell the difference between two images, using a T-shaped maze whose entire floor was electrified, except for a "safety zone" in one arm of the maze. One of the two images sometimes a wasp face, sometimes another image always appeared in the safety zone, though the safety zone itself moved around the maze from one training run to another. The paper wasps learned to identify the "safe" faces faster than other images associated with the safety zone.

The researchers did the same experiment with another, less social type of wasp, called Polistes metricus. In contrast to P. fuscatus, P. metricus didn't learn to identify "safe" faces any faster than the other types of images.

This research appears in the 2 December issue of the journal Science.