Meaningful gestures: electrophysiological indices of iconic gesture comprehension.

To assess semantic processing of iconic gestures, EEG (29 scalp sites) was recorded as adults watched cartoon segments paired with soundless videos of congruous and incongruous gestures followed by probe words. Event-related potentials time-locked to the onset of gestures and probe words were measured in two experiments. In Experiment 1, participants judged the congruency between gestures and cartoons. Gestures elicited an N400-like component (gesture N450) that was larger for incongruent than congruent items, as well as a late positivity that was larger for congruent items. In Experiment 2, participants assessed the relatedness between probe words and preceding cartoon-gesture pairs. N450 effects to gestures were observed without overlapping positivity. These findings suggest that iconic gestures are subject to semantic processes analogous to those evoked by other meaningful representations, such as pictures and words.