It is an open question how similar second-language processing is to native-language processing. One way to measure language processing is through the use of scalp-recorded electroencephalography (EEG). Event-related potentials (ERPs) are specific patterns found in EEG recordings. The P600 is an ERP characterized by a brief increase in voltage 600 ms after a stimulus with an syntactic anomaly like *“He is read his book,” allowing measurement of whether a subject recognizes an error. Learners show native-like P600s quite early, after about 80 hours of classroom instruction. In native speakers, morphologically complex verbs elicit a larger P600 when ungrammatical than monomorphemic verbs. A morphologically complex verb is one made of more than one morpheme, like “eat-ing.” For example *“The sheep should eating,” elicits a larger response than *“The sheep were eat.” Native speakers of Mandarin, unexposed to any other language before age five, will be recruited through the Psychology Subject Pool. They will be presented with English stimuli adapted from a list of 120 sentences in a full 2x2 cross of grammaticality and complexity. Each participant will see one version of each sentence, plus an additional 60 grammatical filler sentences. By averaging across like trials, variance due to possible lexical effects is removed and the effects of grammaticality and complexity are isolated. Presumably, native speakers use the optimal processing strategy, indicated by P600 variability. If learners show variance, it will indicate that their language processing is more native-like. If they don’t, it will indicate that learners at the ability tested do not have access to fully native-like processing. Therefore, I hypothesize that, of the non-native speakers showing P600 responses to verb violations, only the most advanced will show variation, indicating adoption of the optimal processing strategy. Findings will help us understand how new languages are learned, and possibly offer pedagogical suggestions.