Over the course of determining the functional specificity of the N400, it became clear that whereas some types of language manipulations altered the amplitude of the N400, others, including syntactic violations, were associated with different types of ERP effects, such as a later positivity called the P600 or a temporally coincident negativity with a (sometimes left) frontal focus called the left anterior negativity (LAN). A few studies cleverly took advantage of the fact that grammatical violations can have semantic consequences to study syntactic aspects of language with the N400 (reviewed in Kutas & Kluender 1994; Kutas & Van Petten 1994). More commonly, however, this functional dissociation was used to determine how the brain classifies aspects of language about which (psycho)linguists were less certain – e.g., the agreement in gender between a pronoun (her) and its antecedent (the boy), which on some accounts could be syntactic (constraints imposed by one’s grammar) or, by other accounts, semantic (part of each word’s meaning and how they are used in discourse). The ERP results were clear: agreement violations did not modulate N400 activity, but
