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. Here, we tested three species of wild Lamprologine shell-dwelling cichlid fishes from Lake Tanganyika (Neolamprologus multifasciatus, Lamprologus ocellatus, and L. ornatipinnis) that vary in their levels of sociality. We developed a standardized learning paradigm well-established in various species, including cichlids. We used shells, with which the fishes inherently interact, to design an ecologically relevant apparatus to test the three species in identical color 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 white shell. One L. ocellatus and one L. ornatipinnis learnt to choose the correct colored shell in the associative learning task and were further used as demonstrators in the social learning task. In this task, no species showed signs of color stimulus enhancement as the observers’ choices of colors were not influenced by the demonstrators. However, we found evidence for stimulus enhancement at a larger scale as naïve 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 standardized tests in comparative psychology, even across very close species.