OK, here's a really fun one. Paper wasps, the ones that build those paper houses on the side of your house or apartment, have brains that are less than a millionth the size of the human brain, yet new research shows they have an amazing ability to recognize and remember a familiar face, just like folk do (although with a different mechanism). Published in Science (10.1126/science.1211334), one of the premier peer-reviewed, open-literature, journals, the study marks the first time that any insect has demonstrated such a high level of specialized visual learning, says lead author Michael Sheehan, a graduate student working with Elizabeth Tibbetts, evolutionary biologist at the University of Michigan.
“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,” Sheehan says. “That’s surprising and sort of bizarre.”
In earlier research, Tibbetts showed that paper wasps recognize individuals of their species by variations in their facial markings and that they behave more aggressively toward wasps with faces they don't recognize. In 2008, Sheehan and Tibbetts published a paper that demonstrated that these wasps have long memories and base their behavior on what they remember of previous social interactions with the other wasps.
In the current work, Sheehan and Tibbetts trained wasps to discriminate between two different images mounted inside a maze, with one image displayed at each end of the top arm of a "T". Twelve wasps were trained for 40 consecutive trials with photos of normal paper wasp faces, photos of caterpillars, simple geometric patterns, and computer-altered wasp faces. A reward was consistently associated with only one image in the pair at the ends of the "T".
The paper wasps, predators of caterpillars, were able to differentiate between two unaltered paper wasp 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. As wasps' compound eyes are good at detecting contrast and outlines, the wasps should have been able to distinguish the geometric patterns well. However, the wasps learned complicated face images more rapidly than the geometric patterns.
Making even minor changes to a paper wasp facial image with 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 says.
“Humans have a specialized face-learning ability, and it turns out that this wasp that lives on the side of your house evolved an analogous system on its own. But it’s important to note that we’re not claiming the exact process by which wasps learn faces is the same as humans.”
The ability to recognize individuals is important to the survival of paper wasps, in which multiple queens establish communal nests and raise offspring cooperatively, but also compete in a hierarchy of dominance. Remembering who they’ve already beaten and been beaten by keeps individuals from wasting energy on additional aggressive encounters and probably reduces friction in the colony.
A closely-related species of wasp which lacks the varied facial markings of the paper wasp and lives in colonies controlled by a single queen was also tested and scored no better than chance in distinguishing individuals of its own species. “...both species learned to discriminate between pairs of artificial patterns and caterpillars at the same rate and with the same accuracy,” the study says. “...(the two species) differed only in their ability to learn normal face stimuli. “The evolutionary flexibility of specialized face learning is striking and suggests that specialized cognition may be a widespread adaptation to facilitate complex behavioral tasks such as individual recognition.”
Funding for the project was provided by the University of Michigan and an E.S. George Reserve Scholarship to Sheehan.
An important general "learning" from this work is the processing and discriminating power of even a tiny volume of neurons given the necessity to respond to an evolutionary challenge, even a complex one and even in insects.
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