How symbolic gestures and words interact with each other.

Previous repetitive Transcranial Magnetic Stimulation and neuroimaging studies showed that Broca's area is involved in the interaction between gestures and words. However, in these studies the nature of this interaction was not fully investigated; consequently, we addressed this issue in three behavioral experiments. When compared to the expression of one signal at a time, arm kinematics slowed down and voice parameters were amplified when congruent words plus gestures were simultaneously produced (experiment 1). When word and gesture were incongruent, arm kinematics did not change regardless of word category, whereas the gesture induced variation in vocal parameters of communicative and action words only (experiments 2 and 3). Data are discussed according to the hypothesis that integration between gesture and word occurs by transferring the social intention to interact directly with the interlocutor from the gesture to the word.