The Interactions Of Blurredness, Frequency And Semantic On N400in Chinese Characters:Evidence For The IA Model Of N400

Several theories, such as the post-lexical processing theory and prelexical processing theory have been proposed to explain mechanisms of N400. However, there were certain deficits in these theories and in the current paradigm of priming study. So a new approach and new theories to investigate the N400effects are required. The verification model and the interactive activation model were employed in this study to solve the problems. And the question here is, which of these theories provide a much better explanation for the mechanisms of N400. An approach of interaction study was likewise adopted. Two Event-related potentials (ERPs) experiments were included in the study, and in Experiment1English words were used as material, and Chinese single-Characters were used in Experiment2.Experiment1included two factors, which were word frequency and semantic priming. So four conditions were made, which were high frequency (semantic) primed, high frequency unprimed, low frequency primed and low frequency unprimed. The results showed that unprimed items elicited a more negative ERP deflection (N400) than primed items over central scalp regions between400-450ms. A further statistic analysis showed an interaction between word frequency and semantic priming on N400, and the semantic priming effect under low frequency was much larger than high frequency, providing evidence for the verification model and the interactive activation model, but not for the postlexical processing theory.Experiment2adopted a delayed character-matching task to investigate how semantic priming, frequency and blurredness interact on the N400components of the Event-Related Potentials (ERPs), which were recorded while participants committed the task. Three Chinese characters were presented in succession in each trial, representing the prime, the target and the probe stimuli. The prime and the probe were intact characters, while every target was blurred in different Level6(lightly blurred) and Level5(more blurred). All the material was divided into two lists according to the blurred level. The materials and procedures for the two lists were the same. The priming and frequency were manipulated in each list with four treatment conditions, which were primed high frequency, primed low frequency, unprimed high frequency, and unprimed low frequency conditions, while the blureedness was manipulated across lists. So, subjects attended the first list would not did the second list. The subjects’ task was to press one keyboard if the target and the probe were a same character, but press another one if not. The results showed a more negative ERP deflection (N400) for unprimed items than primed items over central scalp regions between400-650ms just as Experiment1. Combining the ERP dates from the two blurred levels, we further found both a three-way interaction among the blurred level, frequency and priming, and an interaction between blurred level and frequency in unprimed condition. Also found was an interaction between blurred level and priming under high frequency, while the interaction between blurredness and priming under the low frequency condition did not happen. These interactions are interpreted as indicating that frequency, blurred level, and priming are involved in the same stage of lexical processing.In conclusion, the results of the present study are partly expected from the lexical verification explanation constructed on the base of the verification model, completely expected from the interactive activation model, but completely unexpected from the postlexical theory.