Evolutionary biologists from University of Michigan found that paper wasps have evolved specialized face-learning abilities analogous to the system used by humans, according to a press release from the university.
A paper wasp queen on an early nest (Michael Sheehan)
“Wasps and humans have independently evolved similar and very specialized face-learning mechanisms, despite the fact that everything about the way we see and the way our brains are structured is different,” said Michael Sheehan, lead author of a paper published in the journal Science. “That’s surprising and sort of bizarre.”
“The study marks the first time that any insect has demonstrated such a high level of specialized visual learning,” said Sheehan.
In earlier research, evolutionary biologist Elizabeth Tibbetts, who worked with Sheehan on the study, showed that paper wasps Polistes fuscatus recognize individuals of their species by variations in their facial markings and that they behave more aggressively toward wasps with unfamiliar faces.
Now, Sheehan and Tibbetts tested learning by training wasps to discriminate between two different images mounted inside a T-maze. Twelve wasps were trained for 40 consecutive trials on each image type. The paired images included photos of normal paper wasp faces, photos of caterpillars, simple geometric patterns, and computer-altered wasp faces. A reward was consistently associated with one image in a pair.
The researchers found that the paper wasps, which are generalist visual predators of caterpillars, were able to differentiate between two unaltered P. fuscatus faces faster and more accurately than a pair of caterpillar photos, two different geometric patterns, or a pair of computer-altered wasp faces. They learned to pick the correct unaltered wasp face about three-quarters of the time.
“Two simple black-and-white geometric patterns should have been easy for the wasps to distinguish, because the insects’ compound eyes are good at detecting contrast and outlines,” Sheehan said. Yet the wasps learned complicated face images more rapidly than the geometric patterns.
At the same time, introducing seemingly minor changes to a P. fuscatus facial image – by using a photo-editing program to remove a wasp’s antennae, for example – caused test subjects to perform much worse on the facial recognition test.
“This shows that the way they learn faces is different than the way they seem to be learning other patterns. They treat faces as a different kind of thing,” Sheehan said.
The ability to recognize individuals is important to a species like P. fuscatus, in which multiple queens establish communal nests and raise offspring cooperatively, but also compete to form a linear dominance hierarchy. Remembering who they’ve already bested–and been bested by–keeps individuals from wasting energy on repeated aggressive encounters and presumably promotes colony stability by reducing friction.
