Wasp Face Processing

Wasp Face Processing Paper Wasp (Polistes fuscatus)
Photo Credit: By Bruce J. Marlin [CC-BY-SA-2.5], via Wikimedia Commons

Paper wasps, which can recognize each other, seem to process faces in ways similar to humans.


Wasps’ facial expertise. I’m Bob Hirshon and this is Science Update.

Paper wasps can recognize each other’s faces. Now, it’s been shown that they also process faces like humans do. University of Michigan behavioral ecologist Michael Sheehan notes that people can tell faces apart better than houses, cars, or other images. But we’re also easily confused when the faces are altered.

By removing parts of the face, people showed deficits in their ability to tell faces apart, or if you can only see part of the face, it’s harder to tell it apart as well. And if you rearrange the parts of the face, people have a really hard time. And we don’t find that same pattern in people when you do that to a different type of object.

His team found the same patterns in paper wasps, but not in another wasp species that doesn’t recognize faces. Sheehan notes that the eyes and nervous systems of wasps and humans evolved independently, and yet when it comes to faces, they seem to have followed parallel tracks. I’m Bob Hirshon for AAAS, the Science Society.

Making Sense of the Research

Humans are particularly good at recognizing faces. Studies show that we can distinguish between different faces more quickly and accurately than other images—for example, pictures of two different houses. It seems that we're hard-wired to pay special attention to faces, which makes sense, given how complex human society is, and how important it is for us to tell individuals apart.

Many animals don't share this ability, but some do. It's fairly uncommon among insects, as far as we know, and even among wasps. However, paper wasps are highly social, and have recently been shown to recognize the faces of other paper wasps, and remember them for at least a week—which, given the lifespan of a wasp, is a pretty long time.

This study, by some of the same researchers, took that knowledge a step further. They wanted to find out if wasps not only could recognize faces, but had a special talent for processing faces better than other visual cues. In the experiment, the researchers taught the wasps to navigate through an enclosed space. At one point, the wasps had to choose between two different paths, each marked with a picture. One side had a reward at the end, while the other didn't. The pictures consistently matched where the reward was. In other words, a particular picture either always appeared in front of the reward path, or it always appeared in front of the wrong path. 

So, the wasp comes to the decision point and looks at both pictures. The pictures were different but belonged to the same category of images: sometimes they saw the faces of two different paper wasps, other times they saw different caterpillars (the wasps' main prey), different simple black-and-white designs, and so on. 

Sheehan's team found that the paper wasps did learn to distinguish between the paper wasp faces faster than the other images. That's similar to what we would expect from humans, and it wasn't true of another wasp species, which is less social and doesn't recognize faces. That suggests that paper wasps are not only capable of face recognition, but that they're wired to recognize other wasp faces in an especially efficient way.

What's more, like humans, the wasps' face recognition system proved especially sensitive to miscues. People, for instance, have a lot of trouble distinguishing between pictures of faces that have been altered in some unnatural way, like removing the eyebrows or tilting the mouth at a strange angle. In contrast, although we're not as good at distinguishing between cars, we also don't get thrown off as easily if the car pictures are altered, for example, by putting the headlights on the side of the car.

The paper wasps responded to face alterations in a similar way. Just removing the antennae from the wasp face pictures was enough to confuse them. Rearranging the facial features also caused a sharp decline in the wasps' face recognition abilities. When the other pictures were altered in the same ways, their performance didn't suffer as much. And for the other wasp species, which doesn't recognize faces, the facial distortions didn't impact their performance any more than distortions to the other pictures.

What's remarkable about all this is that wasps and humans have extremely different eyes and nervous systems, to say nothing of the rest of our bodies. What's more, paper wasps and humans are so far apart on the evolutionary tree that our last common ancestor didn't have eyes at all. So wasps and humans evolved vision independently, and therefore must have developed face recognition independently as well. It's striking, then, that our face recognition abilities would have so many similarities.

Now try and answer these questions:

  1. What's unique about our ability to recognize and distinguish faces, compared with recognizing and distinguishing other images?
  2. How are the paper wasps similar to us in that respect?
  3. How did the design of the experiment show that the paper wasps had a special affinity for face processing?
  4. Why do you think paper wasps and humans are especially confused by pictures of distorted faces, as opposed to other distorted pictures?

You may want to check out the December 16, 2011, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: Why dirty laundry could be damaging the environment, how to make wine growing compatible with wildlife, what the Monarch butterfly genome can tell us about their epic migrations, and how wasps see faces.

The Science Update Averaging Faces delves into the challenges of teaching computers to recognize faces.

For a look at another creepy-crawly but social species, see the Science Update Spider Web Sites.

Going Further

For Educators

The Science Update lesson Averaging Faces delves into the challenges of teaching computers to recognize faces.

For a look at another creepy-crawly but social species, see the Science Update lesson Spider Web Sites.

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