Biting into the truth: unraveling piranhas' cognitive flexibility through reversal learning

Considering how little research has been done on the cognitive system of the Characiformes family, we were motivated to investigate and have a first look into the cognitive abilities of Pygocentrus nattereri. The experiment consisted of an automated colour association reversal learning task divided into two parts: Experiment 1 and 2. In Experiment 1 subjects were required to discriminate between red and green; in Experiment 2, they had to discriminate between white and yellow. We found no evidence of learning capacities after extensive training exceeding one thousand trials overall. We conclude that piranhas may be limited in their capacity to cope with automated operant conditioning devices and call for a further investigation of learning abilities in Characiformes fish.