Preferentially using a certain hand over the other (i.e. handedness) is not only restricted to humans. In costly situations, most vertebrates (and even certain invertebrates) tend to preferentially use a certain side of their body (e.g. hand, foot, eye) to manipulate or get information from an object or their environment (i.e. laterality). The presence of this asymmetry in behaviour is partly explained by its ability to increase cognitive abilities (e.g. multitasking, shorter reaction time when escaping a predator). However, in a population not all members are always lateralised (e.g. ambidextrous) or lateralised in the same direction (e.g. left-handers versus right-handers). The reason for inter-individual variation in laterality is still unclear and is the focus of this study. 

We used a population of three-spined sticklebacks (Gasterosteus aculeatus) looking at their eye preference in a social (a mirror – novel conspecific) and a foraging context. Life-history strategies have been shown to mediate consistent inter-individual differences in behaviour (i.e. personality traits). We therefore investigated whether individuals' boldness (i.e. willigness to explore a novel environment) could explain variation in laterality in these two contexts. 

This study shows for the first time that three-spined sticklebacks are lateralised in both a social and a foraging context. A right eye preference at the population level was found when viewing preys (correlating to previous findings), but inter-individual variation was not correlated with boldness. When observing a novel conspecific, bolder individuals were however found to have a stronger eye preference (i.e. laterality strength) than shyer individuals.