Event-related potential responses to metric violations: rules versus meaning.

In stress-timed languages, the alternation of stressed and unstressed syllables (or 'meter') is an important formal and temporal cue to guide speech processing. Previous electroencephalography studies have shown that metric violations result in an early negative event-related potential. It is unclear whether this 'metric' negativity is an N400 elicited by misplaced stress or whether it responds to error detection. The aim of this study was to investigate the nature of the 'metric' negativity as a function of rule-based, predictive sequencing. Our results show that the negativity occurs independent of the lexical-semantic content. We therefore suggest that the metric negativity reflects a rule-based sequencing mechanism.