Abstract
Synesthesia is a neurological phenomenon by which sensory information are associated to a secondary sensory experience, such as music having color. According to the Developmental Learning Hypothesis (Watson et al., 2010; 2014), synesthesia arises from the need to overcome difficulty in acquiring certain types of information, such as grapheme in the case of grapheme-color synesthesia. Colors are therefore hypothesized to serve as guiding categories to form the new complex ones. In order to test whether colors help forming new complex categories in the general population, we trained two groups of non-synesthetes to discriminate between different musical pitches. The training consisted of an exposure phase followed by a pitch identification phase. For the first group (target group), during the exposure phase seven pitches (C, D, E, F, G, A, B) were auditorily presented in a random manner, along with their respective names. In addition, they were consistently associated to a specific hue category (blue, green, pink, purple, orange, red and yellow respectively). Participants were then tested on a pitch identification task were they heard a pitch and had to press the key corresponding to the name of the pitch. Feedback was provided regarding accuracy. In the control group, the procedure was the same, except that no color was used in the exposure phase. Before and after training, participants completed an absolute pitch test, similar to the pitch identification task, but without feedback. Performances benefited from training as their accuracy on the absolute pitch test improved from 19% correct before training to 54.9% correct after training. Although the target group improved more on average than the control group (59.1% vs 50.5% respectively), the difference was non-significant. However, a longer training might unveil better the effect of color on pitch discrimination, as this training only consisted of 210 trials.