Context-specific response inhibition and differential impact of a learning bias in a lizard.

Response inhibition (inhibiting prepotent responses) is needed for reaching a more favourable goal in situations where reacting automatically would be detrimental. Inhibiting prepotent responses to resist the temptation of a stimulus in certain situations, such as a novel food item, can directly affect an animal's survival. In humans and dogs, response inhibition varies between contexts and between individuals. We used two contextually different experiments to investigate response inhibition in the eastern water skink (Eulamprus quoyii): reversal of a visual two-choice discrimination and a cylinder detour task. During the two-choice task, half of our lizards were able to reach an initial learning criterion, but, thereafter, did not show consistent performance. Only two individuals reached a more stringent criterion, but subsequently failed during reversals. Furthermore, half of our animals were not able to inhibit a pre-existing side preference which affected their ability to learn during the two-choice task. Skinks were, however, able to achieve a detour around a cylinder performing at levels comparable to brown lemurs, marmosets, and some parrot species. A comparison between the tasks showed that reaching the initial criterion was associated with low success during the detour task, indicating that response inhibition could be context-specific in the water skink. To the best of our knowledge, this is the first study to examine inhibitory control and motor self-regulation in a lizard species.