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Researchers in behavioral neuroscience commonly observe the behavior of animal subjects in the presence of two alternative stimuli. However, this type of binary choice introduces a potential confound related to side biases. Understanding whether subjects exhibit this bias, and the origin of it (pre-existent or acquired throughout the experimental sessions), is particularly important to interpreting the results. Here, we tested the hypothesis according to which brain lateralization may influence the emergence of side biases in a well-known model of neuroscience, the zebrafish. As a measure of lateralization, individuals were observed in their spontaneous tendencies to monitor a potential predator with either the left or the right eye. Subjects also underwent an operant conditioning task requiring discrimination between two colors placed on the left–right axis. Although the low performance exhibited in the operant conditioning task prevents firm conclusions from being drawn, a positive correlation was found between the direction of lateralization and the tendency to select the stimulus presented on one specific side (e.g., right). The choice for this preferred side did not change throughout the experimental sessions, meaning that this side bias was not the result of the prolonged training. Overall, our study calls for a wider investigation of pre-existing lateralization biases in animal models to set up methodological counterstrategies to test individuals that do not properly work in a binary choice task with stimuli arranged on the left–right axis.

A large body of experimental evidence suggests that long-term musical training has profound consequences on the functional organization of the brain, leading to an improvement of cognitive abilities that are non-primarily involved in music. Here, we tested the hypothesis stating that long-term musical training has effects in the perceptual laws underlying vision. To achieve our goal, we compared the susceptibility of musicians and non-musicians to the Solitaire illusion, an illusion of numerosity based on the Gestalt law of proximity and good continuation. Both groups were observed in a relative (Experiment 1) and an absolute (Experiment 2) numerosity task: the former required an estimation of which array contained more blue dots; the latter required an estimation of the number of blue dots presented. In both experiments, the illusory pattern was presented as well. In control trials, no difference was found between musicians and non-musicians in the overall performance. The two groups were susceptible to the illusion in both experiments, although the musicians in Experiment 2 varied in their susceptibility to the numerosity misperception, perceiving a smaller illusory ratio compared with non-musicians. Based on these results, we suggest that prolonged music training may alter the perceptual laws in visual modality.

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Several studies in mammals, birds, and fish have documented better cognitive abilities associated with an asymmetrical distribution of cognitive functions in the two halves of the brain, also known as ‘functional brain lateralization’. However, the role of brain lateralization in learning abilities is still unclear. In addition, although recent studies suggest a link between some personality traits and accuracy in cognitive tasks, the relation between anxiety and learning skills in Skinner boxes needs to be clarified. In the present study, we tested the impact of brain lateralization and anxiety-like behaviour in the performance of an extensive operant conditioning task. Zebrafish tested in a Skinner box underwent 500 trials in a colour discrimination task (red vs. yellow and green vs. blue). To assess the degree of lateralization, fish were observed in a detour test in the presence of a dummy predator, and anxiety-like behaviour was studied by observing scototaxis response in an experimental tank divided into light and dark compartments. Although the low performance in the colour discrimination task did not permit the drawing of firm conclusions, no correlation was found between the accuracy in the colour discrimination task and the behaviour in the detour and scototaxis tests. This suggests that neither different degrees of asymmetries in brain lateralization nor anxiety may significantly impact the learning skills of zebrafish.