本研究探討第二語言閱讀者的讀本背景知識對他們從閱讀該讀本中非刻意 學習的詞彙量之影響。過去已有研究者提出被廣泛引用的詞彙閾值作為非刻意 單字學習的前提條件 (Laufer 1989, 2010; Nation 1985)。本研究旨在探討另一因 素的可能性,即文章的背景知識,可以使閱讀者在沒有滿足詞彙閾值的狀況下 也能非刻意的學習單字。背景知識這個變數被設計為在閱讀第二外語(英文) 的文章之前,先閱讀其母語(中文)的版本。受試者為台灣北部大學大一英文 班的學生,其母語皆為中文。在閱讀同一個第二外語(英文)短篇故事之前, 實驗組先閱讀了該故事的母語(中文)版,而對照組手則先閱讀了一個無關的 母語(中文)故事。閱讀任務的結果顯示,實驗組及對照組在閱讀任務中的單 字學習表現有顯著差異,實驗組藉由閱讀而非刻意學習到的單字比對照組多很 多,且此顯著差異不論是在已滿足詞彙閾值的受試者和未達到詞彙閾值的受試 者上均成立。事實上,實驗組中詞彙覆蓋率較差的受試者的非刻意單字學習表 現比對照組中高詞彙覆蓋率的受試者中要好。研究結果指出,詞彙閾值對於是 否能成功達到非刻意單字學習並不是一個必要的決定性因素。閱讀者對於文本 的背景知識也是一個成功的關鍵。;This thesis is an investigation of the effects of L2 readers’ background knowledge of a reading passage on how much vocabulary they learn incidentally from reading that passage. Previous researchers have proposed a widely cited lexical threshold needed as a prerequisite for learning vocabulary incidentally (Laufer 1989, 2010; Nation 1985). This thesis aims to investigate the possibility that another factor, background knowledge of the passage, can enable readers to learn vocabulary incidentally without meeting the lexical threshold. The variable of background knowledge was operationalized as reading an L1 (Chinese) version of the passage before reading it in L2 (English). Subjects were students from a university Freshman English class in northern Taiwan whose reading L1 was Chinese. Before reading the same English short story, the Experimental Group read the L1 version of the story first whereas the Control Group read an unrelated L1 story first instead. The results of the reading tasks show significant differences between the Experimental and Control Groups. The Experimental Group learned significantly more words incidentally from reading the story than the Control Group. This difference held both for participants who met a threshold of known words in the reading passage as well as those who did not meet the threshold. In fact, participants with poor lexical coverage in the Experimental Group showed greater incidental vocabulary learning gains than participants with strong lexical coverage in the Control Group. The findings suggest that the lexical threshold might not be necessary to determine the success of learning vocabulary incidentally through reading. Readers’ background knowledge of the text is also a key to success.