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A Reanalysis of the Handedness-Mathematics Hypothesis Using Generalized Additive Models

Sala et al. (Front Psychol. 2017;8) investigated the impact of handedness on children’s and adolescents’ performance in mathematics in five independent studies (Total N = 2,314). We concluded that (a) handedness played a nonnegligible role in affecting math ability and (b) its effects were mediated by the difficulty of the mathematical task and the participant’s gender and school level (e.g., primary school vs. high school).However, two statistical issues may have biased these findings. First, polynomial regression is a suboptimal (if not incorrect) option for modeling nonlinear relations between variables. Second, simple linear modeling assumes that the response variable is normally distributed in order to produce accurate estimates. However, mathematical performance did not follow a Gaussian distribution in any of the five studies.The present reanalysis overcomes the above methodological limitations by employing Generalized Additive Models (GAMs). While the significant effect of handedness is often confirmed, the GAMs produce somewhat different results compared to the previous analysis. The implications are discussed.