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An ERP Study on the Perceptual Interference Effect

Author: GaoWenHuan
Tutor: WangQuanHong
School: Southwestern University
Course: Basic Psychology
Keywords: perceptual interference Competitive activation hypothesis Mismatch hypothesis N400 Lexical process
CLC: B842
Type: Master's thesis
Year: 2011
Downloads: 84
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Abstract

The perceptual interference effect is the finding that prior exposures to a more degraded stimulus compromise the identification on a less degraded version of the stimulus later. This phenomenon was first demonstrated by Galloway (1946) and subsequently was more systematically investigated by Bruner and Potter (1964). In China, Haidong He and Shulan Jiao (1994)firstly found the perceptual interference effect in Chinese, and recently a series of character studies have further validated and deepened the the perceptual interference effect of Chinese character.Up to now, there are two influential theories which explain this effect:Competitive Activation Hypothesis (Bruner & Potter,1964; Luo & Snodgrass,1994; Snodgrass & Hirshman, 1991) and Mismatch Hypothesis (Wang & Reinitz,2001). The both theories have been verified and supported by several research. They could, to a certain extent, explain the perceptual interference effect well, but they could not give the reasonable explanations to all situations. Notably, the previous studies on perceptual interference were almost all focused on the behavioral experiments. However, a study explored the internal mechanism of this effect on neurophysiological level has not been showed yet. So the aims of this study are to investigate the neurohysiological substrate of the perceptual interference effect and to further explore the underling mechanism of this effect.In additon, in the field of N400 studies, the debate between the post-lexical processing theory and the lexical processing are very fierce. Whether the perceptual interference effect is related to the N400? The study of this question may be another way to resolve the debate. According to the theory of perceptual interference effect, because the hypotheses compete with each other or the mismatch yields inhibition, we predict that the incremental condition will produce a more negative ERP deflection than the standard condition, this negativity is likely to be N400. If so, this study will support the N400 lexical process theory.(1) Experiment 1:ERP study on classic paradigm of the perceptual interference effect. This experiment used the characters which were fragmented at blurredness from Level 1 to Level 5 with a fragmentation procedure of Snodgrass and Hirshman (1991). the aim of this study are to investigate the neurohysiological substrate of the perceptual interference effect and to compare the ERPs that were evoked by he perceptual interference effect with N400 so as to provide the supporting evidence for N400 theories. We expect that the incremental condition will evoke a negative ERP component (N400) which is much larger than the standard condition and the component is relevant to perceptual interference effect. If this hypothesis could be confirmed, this experiment would provide supporting evidence for N400 the lexical processing theory form another perspective.(2) Experiment 2:ERP study on the effect of unfilled interval on perceptual interference effect.This experiment used the same materials as the experiment 1 but we changed the paradigm. We introduced the unfilled intervals into the incremental condition which was as a variant of the standard condition and compared it with he incremental condition, which could avoid the sudden problem of the presence of the stimuli under the standard condition in the experiment 1. Meanwhile, it also offer a new way to explore the perceptual interference effect form another perspective and to test Competitive Activation Hypothesis and Mismatch Hypothesis.Over the two experiments,the results indicate that:(1) There were significant differences between the standard condition and the incremental condition on the N400 and LPC components. Comparing with the standard condition, the incremental condition evoked a more negative amplitude and longer latency N400, and the incremental condition generated the LPC whose the average amplitude of was significantly less than the standard condition. We believed that the N400 and the LPC components were the related components of the perceptual interference effect.(2) Since the perceptual interference effect is the perceptual phenomenon, the N400 which was generated by it is the product of the perceptual processing, the results of this study support the N400 lexical processing theory.(3) Inserting the appropriate unfilled intervals into the incremental condition leaded to the disappearance of perception. The results support the Competitive Activation Hypothesis rather than for the Mismatch Hypothesis.

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