Effects of observing hand motor action on number processing: an online study

In this online study we hypothesized that hand pointing might specifically contribute to the processing of number ordinality, since we learn to list, order, and count series of items through pointing. To test this hypothesis, we asked participants to observe hand pointing or grasping prior to executing number comparison. In experiment 1, participants (N=77) indicated whether a number was larger/smaller than a reference number (magnitude task), therefore processing number cardinality. In Experiment 2, participants (N=75) processed number ordinality, judging whether a number came before/after a reference number in a mental number line (order task). The results showed that response times in the magnitude task (Exp. 1) were faster after grasping as compared to pointing. In the order task (Exp. 2), response times did not differ between grasping and pointing conditions. These results suggest that hand action contribute to specific aspects of numerical processing, in line with embodied accounts of cognition.