Spontaneous grip force fluctuations mirror semantic numerical magnitude processing: Larger numbers elicit larger forces

This study investigated the relationship between semantic numerical magnitudes and motor magnitudes. We asked whether the processing of numbers can affect motor behavior such as the size of numbers affecting the size of motor actions. For this, we recorded continuous grip force fluctuations from 43 healthy adults during a symbolic magnitude comparison task. We found that numbers induced spontaneous grip force fluctuations during number processing. Smaller numbers induced lower grip forces, whereas larger numbers induced larger forces. This result constitutes strong behavioral support for a generalized magnitude processing by continuously quantifying the response that challenges binary accounts of cross-domain interactions.