A new University of Michigan study provides the first evidence of transitive inference, the ability to use known relationships to infer unknown relationships, in a nonvertebrate animal: the lowly paper wasp.

For millennia, transitive inference was considered a hallmark of human deductive powers, a form of logical reasoning used to make inferences: If A is greater than B, and B is greater than C, then A is greater than C.

But in recent decades, vertebrate animals including monkeys, birds and fish have demonstrated the ability to use transitive inference.

The only published study that assessed TI in invertebrates found that honeybees weren’t up to the task. One possible explanation for that result is that the small nervous system of honeybees imposes cognitive constraints that prevent those insects from conducting transitive inference.

Paper wasps have a nervous system roughly the same size—about one million neurons—as honeybees, but they exhibit a type complex social behavior not seen in honeybee colonies. University of Michigan evolutionary biologist Elizabeth Tibbetts wondered if paper wasps’ social skills could enable them to succeed where honeybees had failed.

To find out, Tibbetts and her colleagues tested whether two common species of paper wasp, Polistes dominula and Polistes metricus, could solve a transitive inference problem. The team’s findings were published online May 8, 2019 in the journal Biology Letters.

“This study adds to a growing body of evidence that the miniature nervous systems of insects do not limit sophisticated behaviors,” said Tibbetts, a professor in the Department of Ecology and Evolutionary Biology.

“We’re not saying that wasps used logical deduction to solve this problem, but they seem to use known relationships to make inferences about unknown relationships,” Tibbetts said. “Our findings suggest that the capacity for complex behavior may be shaped by the social environment in which behaviors are beneficial, rather than being strictly limited by brain size.”

The other authors of the new Biology Letters paper—Jorge Agudelo, Sohini Pandit and Jessica Riojas—are undergraduates. Agudelo (2018) and Riojas (2017) were Doris Duke Conservation Scholars.

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The research is being widely covered in the media, including by CNN and the New York Times.