Paper wasps are able to think logically, suggests new study | Biology

A team of researchers from the University of Michigan found evidence of transitive inference – a form of logical reasoning that involves the use of known relationships to infer unknown relationships (if A is greater than B and B is greater than C, so A is greater than C) – in two species of paper wasps: the European paper wasp (Polistes dominula) and metricus wasp paper (Metric Polistes). The study, published in the journal Biology Letters, contributes to a growing body of evidence that miniature insect nervous systems do not limit sophisticated behaviors.

In recent years, vertebrate animals such as monkeys, birds, and fish have demonstrated their ability to use transitive inference.

The only published study that evaluated transitive inference in invertebrates revealed that honeybees were not up to the task. One of the possible explanations for this result is that the small nervous system of honeybees imposes cognitive constraints preventing these insects from carrying out a transitive inference.

The paper wasps have a nervous system about the same size – about a million neurons – as bees, but they exhibit complex social behavior typical of honeybee colonies.

Professor Elizabeth Tibbetts of the University of Michigan and her colleagues wondered whether the social skills of paper wasps could enable them to succeed where bees had failed.

To find out, they tested whether Polistes dominula and P. metricus wasps could solve a problem of transitive inference.

"We are not saying that wasps used logical deduction to solve this problem, but they seem to use known relationships to make inferences about unknown relationships," said Professor Tibbetts.

"Our findings suggest that complex behavioral capacity can be shaped by the social environment in which behaviors are beneficial, rather than being strictly limited by brain size."

To test the transitive inference, the team first collected fluffy queens-queens at several locations around Ann Arbor, Michigan.

In the laboratory, wasps were trained to distinguish between pairs of colors called pairs of premises. One color in each pair was associated with a slight electric shock, and the other was not.

Later, the wasps were presented with pairs of colors that were unknown to them, and they had to choose between the colors. The wasps were able to organize information into an implicit hierarchy and used transitive inference to choose between new pairs.

"I thought that wasps could become confused, just like bees. But they had no trouble understanding that a particular color was safe in certain situations and that it was not safe in other situations, "said Professor Tibbetts.

So why are wasps and bees so different in transitive inference tests?

One possibility is that different types of cognitive abilities are favored in bees and wasps because they display different social behaviors.

A honeybee colony has a single queen and several workers of equal rank. On the other hand, paper wasp colonies have several breeding females called founders. The founders compete with their rivals and form linear dominance hierarchies.

The rank of a wasp in the hierarchy determines the shares of reproduction, labor, and food. Transitive inference could allow wasps to quickly infer new social relationships.

"This same set of skills could allow wasp-tissue women to spontaneously organize information during transitive inference tests," the scientists said.

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Elizabeth A. Tibbetts et al. 2019. Transitive inference in Polistes paper wasps. Biology Letters 5); doi: 10.1098 / rsbl.2019.0015