A group of researchers from the University of Trieste, in collaboration with the CIMeC (Interdepartmental Centre for the Mind and Brain) of the University of Trento, has identified signs of intentional behaviour in insect larvae, traditionally thought to be guided exclusively by reflexes to external stimuli. 

The results of the study, published in Scientific Reports (Nature Group), raise interesting questions about the criteria for attributing intentionality to different animal species, how far we can go - phylogenetically and in terms of the complexity of the neural system - and how far we can recognise forms of volition.

The researchers, in particular, studied larvae of the beetle Tenebrio molitor. Also known as the mealworm, it is the first insect to have been officially approved for marketing in Europe as an affordable, sustainable and advantageous alternative source of protein to traditional ones such as meat and fish.

Cinzia Chiandetti, associate professor of cognitive neuroscience at the Department of Life Sciences at the University of Trieste and head of the Animal Cognition Laboratory: ‘As the results indicate, these animals possess a higher level of cognitive capacity than previously intuited and hypothesised; although they do not imply that all the larvae's behaviour is intentional, they emphasise the complexity of their mental life. They reveal, that is, that these insect larvae - traditionally considered automata, i.e. creatures that would not be able to perform voluntary actions, but would merely respond to external stimuli through reflexes - are capable of articulated decision-making processes, are able to weigh different options, weigh costs and benefits and choose which action to take, demonstrating flexibility to achieve desired results. With a changed and increased sensitivity in the general public to issues such as pollution and environmental impact of intensive livestock farming, anti-speciesism, and animal exploitation, we hope that this discovery will help influence virtuous attitudes in humans.’

In a 3D Y-shaped, specially printed maze (as shown in the figure), the research team trained Tenebrio molitor larvae to prefer one arm to the other in order to gain access to food, observing their ability to learn and, therefore, to head for the side associated with the reward. In the second stage of the study, the researchers applied the so-called ‘reinforcer devaluation paradigm’: i.e. in a different environment, they paired the food with an aversive stimulus, exacerbating it by adding lemon. In a third and final stage, the larvae were tested again in the Y-maze to assess their willingness to choose the target branch where they had received the food reward during initial training. What emerged was that, after devaluation of the reward, the larvae significantly reduced their visits to the target branch: that is, they formed a mental representation of the action-consequence relationship, demonstrating flexible control of actions to obtain desired results and avoid unpleasant ones. 

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Full study published in Scientific Reports

Goal-directed behavior in Tenebrio molitor larvae