Definition:
An event-related potential (ERP) is a measured electrical response of the brain — recorded via electroencephalography (EEG) — that is directly linked in time to a specific cognitive, sensory, or motor event, providing millisecond-level temporal resolution of mental processing stages. In language research, ERPs have been transformative: by presenting language stimuli and averaging the EEG response over many trials, researchers can observe distinct brain responses associated with different aspects of language comprehension — most famously the N400 (semantic processing) and the P600 (syntactic reanalysis). ERPs reveal when different types of linguistic information are processed in the brain.
How ERPs Are Measured
- EEG recording: electrodes placed on the scalp record voltage fluctuations from summed postsynaptic potentials of large neural populations
- Event-locked averaging: EEG is time-locked to a specific stimulus (word onset, sentence completion)
- Signal averaging: averaging across many trials (typically 30–100+) cancels out random neural “noise,” revealing the stimulus-locked component
- Component identification: ERP components are identified by their polarity (positive or negative), latency (time in ms after stimulus), and scalp distribution (where over the head they are largest)
Key Language ERP Components
| Component | Polarity/Latency | Distribution | Functional interpretation |
|---|---|---|---|
| N400 | Negative, ~400ms | Centro-parietal | Semantic processing difficulty / expectation violation |
| P600 | Positive, ~600ms | Parietal | Syntactic reanalysis / morphosyntactic processing |
| LAN (Left Anterior Negativity) | Negative, ~300–500ms | Left frontal | Morphosyntactic violations |
| ELAN (Early Left Anterior Negativity) | Negative, ~100–200ms | Left frontal | Early phrase structure violations |
| Mismatch Negativity | Negative, ~150–250ms | Frontocentral | Pre-attentive phonological change detection |
ERPs and the Syntax/Semantics Debate
A major debate in language processing concerns when and how syntax and semantics interact. ERP evidence has been central:
- The N400 responds to semantic anomalies (and semantic expectation violations in normal language)
- The P600 responds to syntactic violations and reanalysis demands
- The LAN/ELAN are associated with morphosyntactic violations
- Interactions between N400 and P600 speak to whether semantic information influences syntactic parsing (and vice versa)
ERPs and SLA Research
ERPs have been applied to SLA questions including:
- Do L2 learners show native-like ERP patterns for their L2 (or delayed/attenuated responses)?
- Can implicit syntactic learning during L2 acquisition be tracked neurophysiologically?
- Do early bilinguals show different processing profiles from late bilinguals?
Key finding: advanced L2 learners often show qualitatively native-like N400 responses for lexical-semantic processing but sometimes atypical or attenuated P600 for morphosyntactic violations — suggesting that syntactic automatization is harder to achieve in L2.
History
The ERP method was developed in the 1960s. Marta Kutas and Steven Hillyard’s 1980 discovery of the N400 — showing that semantically anomalous words evoked a negative-going waveform — was the landmark moment for language ERP research. Lee Osterhout and Phillip Holcomb’s 1992 discovery of the P600 for syntactic violations established the biphasic N400-P600 framework that has dominated language ERP research since.
Common Misconceptions
- “ERPs show which brain areas process language.” ERPs have excellent temporal resolution but poor spatial resolution — fMRI is needed for localization. ERPs tell when things happen, not precisely where.
- “N400 = sign of error.” The N400 is graded: it reflects processing difficulty/unexpectedness, not a binary error signal. Even a fully grammatical but unexpected word elicits a larger N400 than a highly predictable word.
Criticisms
ERP interpretation is sometimes contested: the same component (like the P600) can be elicited by different types of violations, and the mapping of ERP components onto cognitive processes is not always unambiguous. The field is also constrained by the need for large numbers of repetitions, which affects ecological validity.
Social Media Sentiment
ERPs appear in academic neuroscience and psychology contexts. The N400 is a popular example in science communication for demonstrating that the brain processes meaning with remarkable speed and predictive power. ERP research gets occasional popular attention for findings that link language, music, or mathematics in surprising ways.
Last updated: 2025-07
Practical Application
For language researchers and advanced students, understanding ERP methodology provides critical appreciation for claims about implicit learning, automaticity, and bilingual processing in the SLA literature. ERP evidence is regularly cited in debates about native-like attainment and the critical period hypothesis.
Related Terms
See Also
Research
Kutas, M., & Hillyard, S. A. (1980). Reading senseless sentences: Brain potentials reflect semantic incongruity. Science, 207(4427), 203–205.
The landmark paper discovering the N400 ERP component — showing that semantically anomalous sentence completions evoke a negative-going brain response — establishing ERPs as a core tool for studying language processing.
Osterhout, L., & Holcomb, P. J. (1992). Event-related brain potentials elicited by syntactic anomaly. Journal of Memory and Language, 31(6), 785–806.
The paper introducing the P600 component for syntactic violations, establishing the standard biphasic N400-P600 framework for the ERP study of syntactic and semantic processing.
Kutas, M., & Federmeier, K. D. (2011). Thirty years and counting: Finding meaning in the N400 component of the event-related brain potential (ERP). Annual Review of Psychology, 62, 621–647.
A comprehensive 30-year review of N400 research, consolidating understanding of what the component indexes (semantic prediction/integration difficulty) and surveying its applications across language, memory, and cognition research.