老化及個體差異對於中文代名詞理解之影響：事件相關電位研究

Abstract

本研究旨在探討老化對於中文代名詞理解之影響。代名詞的理解過程涉及代名詞本身與指涉對象之間的關係連結是否能成功建立，但若在文本情境中出現太多或太少可能的指涉對象，都會造成指涉關係理解上的困難。而近來的研究顯示，在面對複雜語句結構或歧義字詞等較耗費認知資源的情況時，語言理解能力的確會受到老化的影響而顯現差異。因此，本研究欲利用事件相關電位(Event-Related Potentials, ERP)技術來探討老化對理解代名詞指涉關係所造成之影響及相關神經電生理機制變化。 本研究操弄代名詞其在句中指涉對象的多寡而形成三種指涉情況：代名詞有兩個可能的指涉對象(指涉關係模糊)、代名詞僅有一個可能的指涉對象(指涉關係明確)、代名詞沒有任何可能的指涉對象(指涉關係失靈)，並記錄年輕人及老年人在理解上述指涉關係時所產生的腦電位變化。 研究結果顯示，年輕組與過去文獻相符，相較於指涉關係明確的代名詞，在處理指涉關係模糊的代名詞時會引發sustained frontal negativity (Nref)，而在處理指涉關係失靈的代名詞時則會引發P600的腦電位變化，且後者存在個體差異，約有三分之一的年輕受試者對指涉關係失靈的代名詞引發負向腦電位變化。另一方面，老年組的資料顯示，相較於指涉關係明確的代名詞，在處理指涉關係模糊的代名詞時並沒有引發sustained frontal negativity (Nref)，卻出現中後區的負向腦電位變化；而在處理指涉關係失靈的代名詞時並沒有顯現任何的腦電位變化，但個別資料顯示，約有一半的老年受試者對指涉關係失靈的代名詞引發正向腦電位變化，另一半則引發負向腦電位變化，因而造成整體腦電位效果的相互抵消。 綜合上述，本研究結果說明，老年人仍有能力處理指涉關係模糊的代名詞，但會有不同於年輕人的神經電生理變化發生，此現象可能來自於伴隨老化的腦部結構及神經機制運用上的轉變；而對於處理指涉關係失靈的代名詞，年輕人及老年人都存有理解上的個體差異，可以不同的方式來解決指涉關係失靈的代名詞，如歸咎於語法或語義上的整合缺失、抑或試圖成立新的指涉對象，因而會造成相對應的腦電位變化差異。

The present study aims to investigate the age effects on comprehension of Chinese pronoun and corresponding electrophysiological changes. Pronoun comprehension involves the establishment of referential relationships between pronouns and antecedents. Sometimes the assignment of a pronoun is difficult since there might be more than one possible antecedents or no possible corresponding antecedent in the context. And recent studies showed that language processes that require more top-down resources, such as processing sentences with complex structure or selecting appropriate meanings for ambiguous words in a context, could be compromised with advancing age. In order to investigate age effects on referential processing, the present study used Event-Related Potentials (ERPs) to examine age differences in Mandarin Chinese pronoun comprehension. We manipulated the referential relations between pronouns and the number of possible antecedents in the sentences such that each pronoun has either (1) two antecedents (referentially ambiguous), (2) one antecedent (referentially unambiguous), or (3) zero antecedent (referential failure). And we recorded younger and older adults’ brain potentials while they were reading sentences in these situations. Our results showed that, consistent with the Dutch findings, relative to unambiguous pronouns, younger adults showed a sustained frontal negativity (Nref) to ambiguous pronouns and a central-posterior P600 effect to referentially failing pronouns. However, there are individual differences in processing referential failure, while the majority of the younger adults showed the P600 effects to referentially failing pronouns, some younger adults showed negativities instead. Older adults did not show the sustained frontal negativity effect to ambiguous pronouns, but a central-posterior negativity instead. On the other hand, older adults as a group showed little P600 effect to referentially failing pronouns but this was due to the cancellation of negative and positive effects we found in individual data. Therefore, our present findings suggest that, older adults are still able to do the resolution of referential ambiguity but with different brain potential patterns compared to younger adults. This may due to the changes on brain morphology or recruitment of neural resources with advancing age. Also, individual differences of processing of referential failure existed in both younger and older adults. People could use different processing strategies to comprehend referentially failing pronouns, such as attributing them to syntactic integration difficulties, semantic integration difficulties, or inventing a new possible referent. These different referential interpretations may mediate the electrophysiological effects in resolution of referential failure situations.