Population lateralisation and social behaviour: A study with 16 species offish

We investigated turning responses in 16 species of fish faced with a vertic al-bar barrier through which a learned dummy predator was visible. Ten of t hese species showed a consistent lateral bias to turn preferentially to the right or to the left. Species belonging to the same family showed similar directions of lateral biases. We performed an independent test of shoaling tendency and found that all gregarious species showed population lateralisa tion, whereas only 40% of the nongregarious species did so. The results pro vide some support to the Rogers (1989) hypothesis that population lateralis ation might have been developed in relation to the need to maintain coordin ation among individuals in behaviours associated with social life.