The learning mechanism underlying public information use in ninespine sticklebacks (Pungitius pungitius).

Elucidating the mechanisms by which animals learn from others is central to understanding the evolution of behavioral adaptations and the constraints that limit options when gathering information about the environment. Here we present findings from three experiments that investigated the psychological mechanisms underlying public-information use in ninespine sticklebacks (Pungitius pungitius). Using a prey patch choice assay we compared two candidate processes, local enhancement and stimulus enhancement. These experiments revealed (a) that fish only selected socially demonstrated prey patches via local enhancement, (b) that even in the absence of any confounding influence of local enhancement there was no evidence for stimulus enhancement in patch choice, and (c) sensitization rather than associative learning underlies the observed public information use. Our findings suggest that local and stimulus enhancement are distinct processes, and that local enhancement is not merely a subcategory of stimulus enhancement, as has previously been argued in the literature. We offer several reasons why learning via stimulus enhancement may not have arisen in ninespine sticklebacks, and speculate that the evolution of this learning mechanism may be favored by specific properties of social structure.