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Endogenous orienting in the archer fish

Significance Volitional orienting, most commonly explored in humans using the classic Posner endogenous cuing task, is often linked to neocortical regions. We applied this task in a species lacking a neocortex (i.e., archer fish). Our study provides a demonstration of facilitation and inhibition of return as a result of a purely endogenous (centrally presented, informative, and symbolic) cue. The results have major implications for our understanding of the evolution of orienting (reflexive and volitional), and for the paradigms used to study “volitional” processes. The literature has long emphasized the neocortex’s role in volitional processes. In this work, we examined endogenous orienting in an evolutionarily older species, the archer fish, which lacks neocortex-like cells. We used Posner’s classic endogenous cuing task, in which a centrally presented, spatially informative cue is followed by a target. The fish responded to the target by shooting a stream of water at it. Interestingly, the fish demonstrated a human-like “volitional” facilitation effect: their reaction times to targets that appeared on the side indicated by the precue were faster than their reaction times to targets on the opposite side. The fish also exhibited inhibition of return, an aftermath of orienting that commonly emerges only in reflexive orienting tasks in human participants. We believe that this pattern demonstrates the acquisition of an arbitrary connection between spatial orienting and a nonspatial feature of a centrally presented stimulus in nonprimate species. In the literature on human attention, orienting in response to such contingencies has been strongly associated with volitional control. We discuss the implications of these results for the evolution of orienting, and for the study of volitional processes in all species, including humans.