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A variety of Polistes fuscatus paper wasp faces. Diagram courtesy Science/AAAS
Article By: Brian Handwerk
for National Geographic News
Published December 2, 2011
Are you one of those people who never forgets a face? You've got some company in the animal kingdom—the wasp.
Scientists have discovered that Polistes fuscatus paper wasps can recognize and remember each other's faces with sharp accuracy, a new study suggests. In general, an individual in a species recognizes its kin by many different means. But faces are extremely important to species such as humans, said study co-author Michael Sheehan, a Ph.D. candidate at the University of Michigan in Ann Arbor.
"Studies show that when you look at a face, your brain treats it in a totally different way than it does other images," he said.
"It's just the way the brain processes the image of a face, and it turns out that these paper wasps do the same thing."
(Related: "A 'Competent' Face Helps Win Elections, Study Suggests.")
Wasp Face-Learning Reaps Rewards
For the study, Sheehan and adviser Elizabeth Tibbetts put wasps of P. fuscatus and P. metricus—a closely related species with a much less complex social structure—in the long stem of a T-shaped maze. Each wasp in the maze was shown two images of faces of other wasps in the same species—one image to the wasp's left and another to its right.
The images "acted like signposts, telling [the subjects] which way to go to get their reward, which in this case was a safety zone," said Sheehan, whose study appears tomorrow in the journal Science.
Though images and safety-zone locations were constantly changed, "one particular image—face A versus face B—was [always] associated with the safety zone," Sheehan explained.
"So they learned, If I go to this face, that's good, but the other face does nothing good for me."
Repeating the maze experiments using simple shapes or other images instead of faces showed that the wasps learned far more slowly and not as well when faces weren't involved—emphasizing the insects' special response to face recognition.
(See "Sheep Are Highly Adept at Recognizing Faces, Study Shows.")
Wasp Face Recognition Helps Keep the Peace
The unique, distinct faces of P. fuscatus wasps, as well as the wasps' ability to recognize and remember each others' faces, are likely tied to the insects' multicolony social structure, Sheehan added.
"They have multiple queens and they all want to reproduce—they all want to be the most dominant. So being able to recognize each other helps them understand who's already beaten who, who has higher ranking in the hierarchy, and this helps to keep the peace.
"When they aren't able to recognize each other, [as] we've shown before, there was more aggression."
(Also see "Alien Wasps Abduct, Drop Ants to Get Food.")
P. metricus wasps, on the other hand, live in single-queen colonies and "don't need to be able to tell each other apart," he said. Not surprisingly, P. metricus wasps look alike and do not show the same ability for face-learning, Sheehan said.
Next, Sheehan hopes to find out how human face perception compares with the ability in wasps. Mammals and wasps have very different eyes, for one thing, and wasp brains are also much smaller and boast far fewer specialized regions.
"We'll be investigating the parallels between primates and wasps," he said.
"There are thousands of research papers on face learning in people, but we're really only beginning to learn about the wasps."