Supplementary material from "Consistency in the strength of laterality in male, but not female, guppies across different behavioural contexts"

Laterality, the division of brain functions into separate hemispheres, is widespread across animal taxa. Lateralized individuals exhibit cognitive advantages yet substantial variation in laterality exists, particularly between the sexes. Why variation is maintained is unknown as few studies consider differences in lateralized behaviours between the sexes, and their underlying selection pressures, across different contexts. We investigated if Poecilia reticulata exhibited sex differences in the direction, strength and consistency of lateralization. We assessed the turning preferences of individuals detouring around a barrier to view visual stimuli representative of different behavioural contexts: an artificial object of familiar colour, an opposite sex conspecific and a no stimulus control. While no sex differences were evident in the direction or strength of laterality, consistency in the strength of laterality varied between the sexes. Individuals of both sexes consistently detoured in one direction, but the strength of laterality exhibited by males was more predictable than females across contexts. This suggests that predictability of lateralization across ecologically relevant scenarios represents a key, but previously unexplored, source of variation between the sexes.