The paper wasp has just entered the very closed circle of animals deemed capable of forming an abstract concept, such as that of the resemblance or difference between two things.
Most species know how to distinguish one essential thing from another, such as good fruit from bad fruit or the cry of a conspecific from that of a predator. Very few are able to form an abstract concept like “same/not the same”, and apply it to different situations.
Primates aside, a small number of species have such a gift, including corvids, pigeons, parrots, dolphins and ducklings. In invertebrates, it has only been listed with the European honey bee.
We must now add Polistes fuscatus, the paper wasp, according to the study published Wednesday in Proceedings B of the British Royal Society.
This social insect is renowned for its ability to distinguish the faces of its congeners without fail. A team of neurobiologists from the American University of Michigan explored its ability to do better.
They first “taught” the wasps to associate a pair of images or smells, similar or different, with a harmless but unpleasant electric current, and the opposite pair with the absence of shock.
Each wasp found itself in a cube whose walls carried, for example, a pair of identical colors. She remained there for two minutes, undergoing an electric current transmitted through the ground, then after a one-minute pause, she was placed in another cube, without current, where there was a pair of different colors from each other. other.
– Less than a million neurons –
The pairs of stimuli, colors, wasp faces or smells, were changed between each session so that the animal did not associate a particular pair with the electric shock.
After four learning sessions and a break of three quarters of an hour, the wasp underwent a test supposed to check if it had integrated the notion of “same/not the same”.
She was placed in a box where she had the choice between moving towards an extremity carrying an identical pair of stimuli or towards one carrying different ones. The right choice consists in heading towards the pair of stimuli associated in his experience with the absence of an electric shock.
At first, the kind of stimulus, -color, face or smell-, was identical to that of the learning phase but not the stimulus itself, the color changed for example. After ten trials, and a new pause, the experiment was repeated with a kind of stimulus never encountered by the animal, such as the smell after the colours.
In both cases, the wasp passed the test with more than 80% success, well beyond luck alone. A result completely independent of the kind of stimulus involved.
And a feat considering that the brain of this wasp, like that of the European bee, has less than a million neurons, when that of the pigeon exceeds 300 million and that of the macaque six billion, note the researchers. And which makes them think that the learning of the concept “same/not the same” is perhaps more widespread among insects than anticipated.
Beyond that they conclude that the “miniature nervous system of insects does not impose a limit on the sophistication of their behavior”, according to the study.