BLOOMINGTON, Ind. — A wasp may be the first invertebrate shown to have a special talent for learning faces of its own kind.
Like people, Polistes fuscatus wasps can tell apart individuals from their species. It turns out that these wasps are especially good at recognizing faces compared with other objects, Michael Sheehan of the University of Michigan reported July 28 at the Behavior 2011 conference.
“To my knowledge, no other insect has yet been shown to have such specialized face learning for individual recognition,” said evolutionary biologist Emilie Snell-Rood of the University of Minnesota. Studying how individuals of any species recognize each other enriches the understanding of a species’ social scene.
Biologists have debated whether certain species — including people and some other primates, as well as sheep — have some specialized cognitive power for interpreting faces. Now, it seems, the discussion will spread to wasps.
In P. fuscatus colonies, wasps sport irregular patterns of yellow, brown and black markings. Recognizing each other’s quirky face markings seems to minimize aggression as queens clash for dominance when establishing joint nests.
Sheehan and his colleagues tested the wasps’ ability to learn by teaching them to choose one out of a pair of wasp faces versus one out of two abstract black-and-white patterns or one in a pair of caterpillar portraits. Researchers tested multiple pairs in each category.
The P. fuscatus wasps learned to select between images of all three types. Yet the six-legged students scored highest when learning to pick out the correct wasp face, getting the right answer in about three-quarters of tests.
As further evidence that faces themselves are special to paper wasps, the insects did better at distinguishing images of real faces and not as well in learning images with face elements mashed together in unnatural clumps or with their antennae blanked out.
Sheehan also tested a different species, P. metricus, and did not find signs of any special reaction to faces. But P.metricus has neither the variety of face markings of P. fuscatus, nor do colonies have more than one queen.
The contrast with P. metricus makes a particularly striking part of the case, said David Queller of Washington University in St. Louis.
Tested on the not-very-different faces of their own kind, P. metricus wasps didn’t score above chance in learning to choose between pairs. They did learn to distinguish between the variable faces of P. fuscatus. But their performance didn’t differ from learning jumbled mashups of face parts or antenna-free faces. For them, Sheehan concludes, a face really is just another object.
