Lateralization of detour behaviour in poeciliid fish: the effect of species, gender and sexual motivation.

We studied detour responses of two species of poeciliid fish (Gambusia hoolbroki and Girardinus falcatus) faced with a vertical-bar barrier, through which conspecifics of the same or different sex or a simulated-predator (which induced detour behaviour for predator-inspection responses) were visible. Both species showed a consistent bias to turn leftward when faced with the predator, and a consistent bias to turn rightward when faced with an opaque barrier. Sexual stimuli (conspecifics of different sex) elicited a leftward bias in females that had been deprived of the presence of males for 2 months, whilst no bias was apparent in non-deprived females. Social stimuli (conspecifics of the same sex) elicited a consistent rightward bias in females but not in males in both species. Results suggest that males and females of both species show basically the same pattern of laterality and that sex differences, when present, can be accounted for in terms of differences in sexual and/or social motivation.