語義優勢性對語法語境中詞彙歧義解析之影響—中文歧義詞處理的事件相關電位研究

Effects of Meaning Dominance on Lexical Ambiguity Resolution in Syntactic Context— An ERP Study of Homograph Processing in Chinese

曹景瑄(Ching-Hsuan Tsao)

指導教授 ： 李佳霖

國立臺灣大學/文學院/語言學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201900681

摘要

過去的文獻指出，能夠影響詞彙歧義解困(lexical ambiguity resolution)的兩大主因為語義頻率(meaning frequency)和語境訊息(context)。過去研究皆認為語境訊息的存在能有效地幫助選擇適當的語義進而達成語義消歧，然而語法和語義語境是否皆能影響一開始語義的提取似乎仍未明朗。單純操弄語法語境的研究多半未特別區分同形異義詞(homograph)中主要語義及次要語義的語義頻率，而且實驗間採用不同的典範如促發典範(priming paradigm)的詞彙判斷作業(lexical decision task)以及方法如眼動追蹤技術(eye-tracking)、事件相關電位(Event-Related Potential, ERP)有可能引發不同的反應策略。有鑑於此，本篇論文欲以中文為媒介來探討兩項議題：（一）語法語境是否能影響中文非均勢同形異義詞(biased homograph)中語義之提取；（二）語義優勢性在中文詞彙歧義解困處理歷程中是否能與語法語境互動。並以事件相關電位(Event-Related Potential, ERP)技術來做為此議題的實證。
詞類歧義詞提供一個媒介來檢驗語義優勢性在語法單獨存在之語境下進行詞彙歧義解困的作用。實驗一我們將兩種不同類型的中文非均勢同形異義詞置於只有語法訊息但語意短缺的中文短語內，僅根據語法提示(syntactic cue)來提取非均勢同形異義詞中的主要語義或次要語義為最適當的語義解讀。由於實驗一整體效果不如預期顯著，實驗二為實驗一之改良，沿用相同材料，並搭配語義關聯性測驗(semantic relatedness judgement task) 使受試者更需要整合語境以及歧異詞，同時受試者須做兩個實驗列表以利檢視實驗一中觀察到的個體差異。
研究結果顯示，過往文獻中提到涉及詞彙歧義時會引發在前區持續的負向效果(frontal negativity)在整體的受試者中效果並不明顯，但在閱讀經驗較高的受試者上較為突出。此結果可能表示個體對於解歧語境有反應差異且體現於閱讀能力之指標。根據中位數分組的結果顯示，閱讀經驗較高的受試者在歧義詞上引發負向腦電位變化，另一半閱讀經驗較低的則引發正向腦電位變化，因而造成整體腦電位效果的相互抵消。另外，我們也在閱讀能力較高的組別中發現負向的歧異效果主要出現在當語法語境導向中文非均勢同形異義詞的次要語義，範圍由頭皮前區延續到中後區。然而當語法語境導向主要語義時，除了與語義關聯的N400短暫出現外，負向的效果似乎較不明顯。整體而言，本研究的結果顯示，語法訊息語境能夠提供促進語義提取進而幫助解歧，且其受到語意優勢性的影響。當語境導向主要語義時，主要語意可以被迅速且強烈的提取，次要語意即便有被提取，其所形成的語義競爭甚小，意義選擇不須額外的上到下的資源即可語義競爭透過較為自動化的意義模式（顯示在N400的效果）順利完成解歧。然而，當語境導向次要語意時，由於次要語意的提取受到語境的支持，且主要語意的提取還是非常強烈，因而形成強烈的語義競爭，需要由一上而下的處理歷程來幫助解歧。過去文獻顯示動用此資源的能力有個體化的差異，本研究的結果與此一致，顯示擁有較好的閱讀能力者較容易啟動此協助解歧的機制。

關鍵字

一詞多義 ； 詞類歧義 ； 語境 ； 語意優勢性 ； 詞彙歧義解困 ； 個體差異 ； 事件相關電位

並列摘要

In general, past literature has indicated that meaning dominance and context are the two main factors influencing lexical ambiguity resolution. Prior research suggested that context can help select contextually-appropriate meaning effectively, and thus succeed with lexical ambiguity resolution. However, it seems less evident whether the initial meaning access could be influenced by the context with only syntactic information. For one thing, most studies manipulating the syntactic information context alone did not distinguish the meaning dominance of the dominant and subordinate meaning of homographs specifically. For another, various paradigms adopted in different experiments such as priming with lexical decision task, eye-tracking, and event-related potential were likely to reflect different response strategies. In view of the above-mentioned facts, the present study targeted Chinese native speaker to investigate (1) does syntactic context affect meaning access of Chinese biased homographs, and (2) does syntactic context effect interact with meaning dominance. We used Event-Related Potential (ERPs) to examine the brain responses and attempt to make an empirical study.
Syntactic category ambiguous words, whose alternative meanings differ in syntactic categories (e.g., trip in English), serve as a means of examining this issue. In Experiment 1, two types of Chinese biased homographs (i.e., NV and VN homographs) were embedded into phrases in which syntactic information provided but lack of semantic. That is, either the dominant or the subordinate meaning of homographs would be extracted to be the contextual-appropriate meaning depending only on syntactic cues. On account of the more insignificant overall effect than predicted in Experiment 1, Experiment 2 adopted the same materials but replaced with the semantic relatedness judgement task to make participants further integrate the contexts and homographs. Meanwhile, all participants were required to do two experimental lists to examine the individual difference observed in Experiment 1.
Our results showed that the overall ambiguity effect was not as prominent as that in the previous studies which have found an ambiguity-related sustained negativity at frontal regions, the effect was more obvious in the subjects with high score of reading experience instead. It might indicate that individual differed in reaction to the disambiguated context, and such an individual difference may manifest on reading abilities. Based on the result of grouping data with median split, participants with higher scores on reading experience showed a sustained negativity relative to unambiguous words, and half with low scores showed a positivity, and thus cancelled out the overall ambiguity effect.
On the other hand, in the high score group of reading experience, we found a clear negativity showed when the syntactic context favored the subordinate meaning of homographs, ranging from frontal scalp to central-posterior, whereas when the syntactic context picked out the dominant meaning of homographs, except for the transient N400 effect related to semantic access, it seemed an absent sustained negativity. In sum, this current study indicated that the syntactic context is able to affect the meaning access and help disambiguation, yet such context effect is modulated by meaning dominance. In the dominant-biasing context, the dominant meaning could be accessed intensely and rapidly, and the meaning competition is thus very small even if the subordinate meaning is activated. Such a process of meaning selection can be accomplished through a model of meaning automation (displayed on the N400) and thus reach disambiguation successfully. On the contrary, despite the fact that the subordinate-biasing context supports the activation of subordinate meaning, the access of dominant meaning is still robust at the same time. Hence, a strong meaning competition is generated, and an additional mechanism is necessary to be involved to help. As suggested by past literature, there is an individual difference for mobilizing the top-down resources, which is consistent with our result that those who have better reading abilities are more likely to initiate the kind of mechanism.

並列關鍵字

homograph ； syntactic category ambiguity ； context ； meaning dominance ； lexical ambiguity resolution ； individual difference ； Event-Related Potential

參考文獻

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