INTRODUCTION: In biomedical research, there is a constant lookout for animal models that can help in the search for new drugs and therapies. The most commonly used are laboratory mice and rats, but their use is under pressure of the need to reduce used animals. Many experiments can be performed on simpler vertebrates such as fish, but even here the choice of species is crucial. METHOD(S): I used a comparison between the same types of experiments conducted on fish and other groups of animals based on published data. RESULTS: Regarding complex cognitive mechanisms, there is experimental evidence for diverse processes such as cognitive maps, transitive inference, complex social learning rules, referential gestures, generalization, or mirror recognition in fish. Recent research on vertebrate brains has also identified amazingly conserved structures with respect to a so-called social decision-making network, which consists of the ‘social behaviour network’ and the ‘basal forebrain reward system’. CONCLUSIONS: Given these similarities, fish seem to offer vast opportunities for testing general principles concerning social behavior and underlying cognitive mechanisms and processes. There is also a need to create special equipment to study more sophisticated behavioral tasks in fish that could be compared with that of rats and mice. Additionally, behavioral tests combined with the analysis of the brain structure will allow us to understand the differences in processing information concerning social and environmental behaviors.