Experimental study of social learning in three wild shell-dwelling Tanganyikan cichlids that vary in sociality

The social intelligence hypothesis posits that animals living in more complex social groups display better cognitive performances. However, this hypothesis has mainly been investigated in primates and studies using similar paradigms across different species are scarce. We tested three species of wild Lamprologine shell-dwelling cichlids from Lake Tanganyika (Neolamprologus multifasciatus, Lamprologus ocellatus, and Lamprologus ornatipinnis) that vary in their levels of sociality, in identical colour associative learning and social learning tasks. We found species differences in engagement in the training for these tasks and only 5 out of 24 individuals learnt to feed from a neutral object (a shell). One L. ocellatus and one L. ornatipinnis learnt to choose the correct colour in the associative learning task and were further used as demonstrators in the social learning task. In this task, no species showed signs of colour stimulus enhancement as the observers choices of colours were not influenced by the demonstrators. However, we found evidence for stimulus enhancement at a larger scale as naive observers approached the novel experimental apparatus faster than the demonstrators when first exposed to this apparatus. Our results encourage further research of social learning processes in individual fishes and highlights the difficulties in using identical paradigms in comparative psychology, even across very close species.