Can three-spined sticklebacks learn when to display? Rewarded displays

Abstract

Learning when and how to perform displays could be important for the development of normal aggressive behaviour. This paper examines the effects of associating threat displays with the disappearance of an opponent in three-spined stickleback fish, Gasterosteus aculeatus. It was predicted that making the opponent ‘go away’ each time the test subject displayed should reward the use of head-down threat: trained fish should increase the probability of threat relative to other aggressive acts. Threat became more common and was more quickly used by rewarded fish. Continuous-time Markov chain models of the sequence of actions showed that the relative chance of changing from other acts to the threat display was increased in reinforced fish. However, none of the changes was outside the range of normal variation seen in untrained individuals.