Experimental And Theoretical Research On N400 Lexicality Effects In Chinese Two-character Words

Language is an important function of the human brain, and it plays an important role in people's social interaction, individual cognition and personality development. Because of this, lots of scholars have studied the Language cognition processed and obtained a great deal of research outcomes. Especially with the technology of the modern electrophysiological event-related potentials (ERPs), research has greatly promoted the understanding on language cognition of the brain. N400 is a ERPs component which closely related to language cognition of the brain, a lot of psychological research on language were acquired through research of the N400.N400 was first found by Kutas and Hillyard in 1980. After that, many researchers adopted different verbal stimuli, such as unrelated and related words, nonwords (pseudowords) and real words, old and new words and so on, also observed the classical N400 component. In these studies, researchers'interest was not limited on the conditions eliciting the N400, and paid much attention in exploring the relationship between the N400 and language cognition process. Currently, there are three main N400 theories of explaining the relationship between the N400 and the underlying language (cognition) process of the brain, which are the Post-lexical Processing Theory, the Pre-lexical Processing Theory and the Lexical Processing Theory. These three N400 theories differ in holding that the N400 reflects different stages of lexical processing, No even a common conclusion has yet been reached about what stage of lexical processing the N400 reflects.The present study reviewed lots of prior studies about N400 and its mechanism in language process, and on the base of these previous studies, this study attempt to put forth a N400 lexical verification view to address the language cognition processes underlying the N400, which also expends Becker's lexical verification model. Chinese two-character words and pseudowords were adopted to investigate whether the N400 lexicality effect (Pseudowords elicited a greater negative N400 compared with real words) was induced by the number of lexical verification circles required to identify a verbal stimulus.To examine the N400 lexical verification view versus the post-lexical views, two experiments as follow were conducted in this study.(1) Experiment 1:The experiment of pseudowords versus opaque words on N400. Chinese two-character opaque words and pseudowords were adopted to investigate whether the N400 lexicality effect was induced by the number of lexical verification circles. In other words, when pseudowords and opaque words were matched for the semantic relationships between constituents and the whole word, would the N400 lexicality effect (The pseudowords elicited more negative N400 amplitude compared with opaque words) occur? If the pseudowords elicited more negative N400 amplitude compared with opaque words, which would provide evidence for the N400 lexical process theory and the N400 lexical verification view; but if the N400 lexicality effect didn't occur, no evidence would be provided for post-lexical process theory.(2)Experiment 2:The experiment of derived pseudowords versus real words on N400. A new type of pseudowords will be adopted in this experiment. This new pseudoword, which were each formed by changing the constituent order of the opaque word root, were called derived pseudowords to be distinguished from the pseudowords used in Experiment 1. The derived pseudowords and the opaque words not only have the same semantic relatedness between constituent characters and the whole-word as in Experiment 1, but also have the same semantic relatedness between the constituent characters and the same association between the constituent characters. If, in this situation, N400 amplitude is still greater for derived pseudowords than for opaque words, the semantic relatedness and/or association would not account for the N400 lexicality effect found in Experiment 1 via post-lexical integration. This result would thus provide further evidence for the lexical verification view.Over the two experiments, the results indicate that:(1)N400 lexicality effects existed for Chinese two-character real words versus pseudowords, and regardless of whether the words were opaque or transparent and whether the pseudowords were regular or derived.(2)When the difference between (opaque) words and pseudowords in characters'semantic relationship and association were further gotten rid of with special (derived) pseudowords replacing the regular (nonderived) pseudowords. Specifically, the N400 amplitude elicited by the derived pseudowords is greater than opaque words. This finding provided more compelling evidence for the lexical verification view but against the post-lexical account.(3)The lexical process account, which is distinguished from the verification view, cannot completely been used to explain the underlying process mechanism of N400 in Chinese compound words. In this study, the verification model can properly interpret the underlying process of N400 in Chinese compound words in a new prospect.