Factors affecting the measure of inhibitory control in a fish (Poecilia reticulata).

Inhibitory control allows an individual to block automatic responses as well as to control behaviour and attention. There is growing evidence that many species possess this ability, although the difference in performance among species is great. Inhibitory control has been frequently measured using the detour task: a desired reward is placed behind a transparent barrier, and the animal has to inhibit the tendency to directly move toward the goal, instead making a detour around the barrier. Mammals' and birds' inhibitory performance varies according to several factors, such as the distance from the reward and its value, and in dogs, the breed also affects it. We investigated whether these factors affected performance in a fish, the guppy (Poecilia reticulata), by using the detour task, with reaching a social group as goal. We found that guppies were more proficient in making a detour around the barrier when the goal was far, but the value of the reward (i.e., the size of the social group) had no effect. We also found a clear effect of strain, with the guppies that descended from a wild population performing better than the domesticated guppies. Our study revealed that some of the factors affecting inhibitory control in warm-blooded vertebrates also modulate the performance of fish. These factors should be taken into account when comparing this function across species.