Can you touch the N400? The interactive effects of body-object interaction and task demands on N400 amplitudes and decision latencies.

The effects of semantic richness on N400 amplitudes remain unclear. Some studies have reported semantic richness evoking greater N400s, whereas others have reported the opposite effect. Moreover, N400 effects of some semantic richness variables, such as body-object interaction (BOI), have yet to be demonstrated. BOI quantifies the degree to which a word's referent is easy to interact with; words such as bicycle are high-BOI whereas words such as butterfly are low-BOI. We examined BOI effects on N400 amplitudes and decision latencies in two semantic tasks. We found that in a touchable/untouchable task, low-BOI words (e.g., butterfly) evoked greater N400s than high-BOI words (e.g., bicycle), but there was no difference in decision latencies. Conversely, in a concrete/abstract task, high and low-BOI words evoked similar N400s, but decision latencies were shorter for high-BOI than for low-BOI words. Our results show that semantic richness upstream and downstream effects are dissociable and task dependent.