Wasps reason like we do

11 May 2019


A European Paper wasp


Paper wasps are capable of “transitive inference”, a cognitive skill previously thought to be unique to human beings, a new study confirms...

Transitive inference refers to the ability to use information about things you know, to draw conclusions about things you don’t know. For example, if you know that A is bigger than B, and B is bigger than C, you can infer that A is bigger than C, without having to see the two side by side.

“Long ago people thought that transitive inference was based on logical reasoning, and we thought that only humans were capable of transitive inference”, reports wasp specialist Elizabeth Tibbetts, from the University of Michigan. But, over time, we’ve learned other vertebrates like monkeys, birds, and even some fish can do it too.

Previously, work in honey bees has shown that they are incapable of employing transitive inference. But Tibbetts and her team wanted to know if the much maligned wasp is indeed more cunning than its bumbling honey-making counterpart.

“We trained them to a bunch of colours,” explains Tibbetts. “For example, we would train them that blue is better than green; and then we would train them that green is better than purple.”

The researchers then prompted the wasps to choose between pairs of colours that they hadn’t seen together before: blue and purple, for instance, to see if they were capable of ordering the various colours in their minds and making the correct choice.

But how do you teach a wasp that blue is better than any other colour?

“We train them in this tiny little maze... some of the bottom is electrified, and then some of the bottom isn’t. When we’re training them that blue is better than green, blue is a safe area in the maze and green gives them a little electric shock,” explains Tibbetts, emphasising that “no wasps were harmed”, given that the electric shocks are extremely mild - just enough to get them moving!

After training, it was test time. The electricity was taken away and the wasps were presented with pairs of colours - some they had been trained on, and some they had never seen together.

“We found that wasps do have transitive inference - they took all those trained pairs and seemed to organize them in their mind linearly and choose between stimuli.”

This was slightly surprising, given that bees and wasps have similar size brains, but bees are not capable of using this skill.

Tibbetts theorises that this difference comes down to the kinds of social lives the animals lead.

“All the workers on a bee colony are about the same...but wasps have a linear dominance hierarchy.”

It is important for a wasp to be able to figure out where it sits in the social hierarchy of the colony - which can determine allocation of work and distribution of resources. Transitive inference may help wasps to figure out their place.

“If you’ve beaten Jane in a fight before, and you see Jane beat Susan, then you can infer - ‘Hey, I’m probably going to be able to beat Susan.’ ”According to Tibbets, this as an example of the fact that animals can be extremely skilled at complex tasks, provided that task helps the animal in some way.

“You don’t need a big brain to do complicated things! Even a tiny little brain can do complicated things, if an animal needs to be able to do it.”

The fact that wasps have advanced cognitive skills might not be exciting for you if you aren’t a fan of the little creatures, but it’s certainly a fascinating result for the world of animal psychology!


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