近年來許多研究討論脈絡限定性(contextual constraint)的強度以及目標詞的可預測性是如何影響閱讀理解的過程，此外Wlotko and Federmeier(2007)的研究也提出左右半腦運用或處理脈絡訊息的模式不同也影響閱讀理解的結果。然而過去研究定義脈絡限定性的效果都與名詞的克漏字機率(cloze probability)共變，所以難以區分實驗所得到的效果是來自於脈絡限定性或是克漏字機率。本研究藉由中文分類詞與可接名詞的語意關係，重新探討脈絡限定性與目標詞可預測性對閱讀理解的影響。研究首先建立分類詞的資料庫，以資料庫中連接廣度為分類詞限定性強度的指標，解決與克漏字共變的問題。實驗一旨在探討脈絡限定性如何改變概念整合的情況。實驗結果發現，N400的部分得到強限定性的情境下，可預測性低的目標詞引發較負的N400，顯示限定性會改變目標詞語意整合的難易度的結果。實驗二進一步探討左右半腦如何運用脈絡訊息進行語意整合。結果支持Wlotko and Federmeier(2007)對於左右腦處理模式的假設。認為左腦的處理模式是一種預測性的歷程(predictive process)，左腦會先行運用脈絡訊息形成的預期，因此在早期P200的詞彙處理階段與N400的地方得到限定性對語意整合的難易度的影響。而右腦的處理則是一種整合性的歷程(integrative process)，主要處理詞彙的關聯性，實驗結果得到N400的波形主要反應目標詞可預測性的影響，不受限定性影響。綜合實驗結果，脈絡限定性的強弱會影響詞彙處理的效能，而左右半腦會以不同的處理模式運用脈絡訊息，可說語言理解過程是左右半腦共同合作的結果。Although a large body of literature has demonstrated that the context affects word processing. Moreover, studies have been showed the cerebral hemispheres are differentially sensitive to sentence-level information, which implicate for normal language processing. Previous studies examined the joint effects of sentential constraint and expectancy (cloze probability) on the ERP responses to words and suggested that there were multiple effects in different processing stages. Nevertheless, cloze probability under strongly and weakly constraining context is not well matched in those studies, which makes the interaction between context and cloze probability unexplainable. The current study aims to reexamine this issue by using the characteristics of Chinese classifier-noun agreement. First, we established a database for 180 Chinese classifiers. Each of them was rated according to their familiarity, strength of constraint (the number of nouns that can be followed by a specific classifier) and the cloze probability for those following nouns. In the first ERP experiment, each participant will perceive a highly expected (high cloze probability), an unexpected (low cloze probability), or an anomalous noun followed by either a strongly constrained or weakly constrained classifiers. The data showed the interaction of contextual constraint and cloze probability in N400. The critical comparison between unexpected nouns of low cloze probability and anomalous completions showed different patterns in strongly and weakly constraining context. The result is interpreted as that, the strongly constrained context yields a narrower scope of activation than weakly constrained context does. The difference in the responses to them might be a cause of the presence of a preferred competitor in the strong constraint condition. Thus, additional resources might be needed to override or suppress a strong prediction for a different word or concept. In the second experiment, the targets were presented at two visual fields separately. The result support the suggestion that only the left hemisphere (LH) makes predictions about upcoming items. Targets in strongly constrained classifier elicited larger P2s, and N400 responses the interaction between constraint and cloze probability. In contract, the right (RH) processes words in a more integrative fashion. N400 showed the typical pattern of amplitudes graded by cloze probability without the influence from constraint. These data point out the multiple effects and highlight the importance of hemispheric asymmetries and their implications for normal language processing.
