Role of an ideomotor mechanism in number processing.

The ideomotor principle predicts that the anticipation of expected sensory consequences precedes and controls voluntary goal-directed movements. Recent studies have revealed that an ideomotor mechanism could also support the link between finger movements and number processing. However, it is unknown whether such a mechanism is devoted to number processing per se, that is, without associated movement. In three experiments, we tested whether the ideomotor mechanism was also involved in a verbal number production task without associated goal-directed and motor dimensions. We tested this hypothesis in a response-effect (R-E) paradigm generally used to assess the ideomotor mechanisms. The results of Experiment 1 revealed a compatibility effect both in a stimulus-response task and an R-E task, suggesting the involvement of an ideomotor mechanism during number processing. More importantly, Experiment 2 revealed that performance in a motor imagery task correlated with the R-E compatibility effect, whereas performance in a visual imagery task did not, suggesting a distinct motor imagery contribution to R-E compatibility. Finally, Experiment 3 showed a strong R-E compatibility effect in a verbal word production task, but the correlations with motor or visual imagery tasks were not observed. Altogether, these findings suggest that ideomotor mechanisms play a specific and functional role in number processing.