Behavioural and neurophysiological evidence of semantic interaction between iconic gestures and words

We report two experiments that provide converging behavioural and neurophysiological evidence on the relationship between the meaning of iconic gestures and words. Experiment 1 exploited a semantic priming paradigm and revealed interference between gestures and words when they were not related in meaning, but no facilitation when they were. This result was confirmed in Experiment 2, where ERPs were recorded during silent word reading with the same paradigm. The analysis showed a negative deflection peaking near 400 ms (N400) and, in the left hemisphere, greater negative values for verbs than for nouns. Differently from the classical distribution obtained with verbal stimuli, we found an N400 that spread more over central-anterior areas of the scalp, suggesting that the meaning systems of gesture and language do not overlap completely. These results are consistent with the view that the meaning systems for gesture and speech are tightly integrated.