Do musicians perceive numerosity illusions differently?

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.