Comparing Brain Responses to Moral and Semantic Violations

The processing and evaluation of behavior, actions or events that go against social (moral) norms can be assumed to operate on mental representations of the world and of how people typically behave. These mechanisms and representations may therefore be shared by the processing of meaning in general. The current study investigated whether the processing of deviations of morality can be distinguished from processing of semantic inconsistencies.

Event-related brain potentials (ERPs) were recorded from English speakers while they read short written texts in English for comprehension. Texts contained words that constituted moral violations, semantic violations and neutral controls depending on the context, allowing for a direct comparison.

Using trial-based analyses, we found different ERP responses to semantic and moral violations: the moral violation elicited a long-lasting, posterior Late Positive Component (LPC) starting at around 300 ms, whereas the semantic violation elicited a positivity that started later and was descriptively more frontally distributed. Furthermore, the LPC amplitudes could be explained by the moral acceptance scores over and above plausibility scores, but not vice versa.

The outcomes are compatible with the view that the processing of moral deviations engages at least some mechanisms that are different from the processing of semantic deviations.