本論文探討五歲漢語兒童情態詞習得的情形。實驗一利用隱藏盒子實驗(Hidden Box Task)探討五歲兒童對於認知情態詞(epistemic modal)「可能」和「一定」的理解。實驗結果顯示，兒童在確定情境(the determined condition)下表現與大人無異，然而在不確定的情境(the undetermined condition)下則非如此。兒童有正向偏誤(positive bias)及不成熟的結論(premature closure)的傾向都顯示出他們在不確定的情境中有認知上的困難。和Moscati & Crain (2014)和 Moscati, Zhan,& Zhou (2016)的研究綜合來看，我們推論語言中情態詞的數量對於兒童學習情態詞是有影響的。實驗二探討五歲兒童是否有等級隱涵(scalar implicature)的語用能力。實驗結果顯示，兒童無法在隱藏盒子實驗(Hidden Box Task)中，展現出等級隱涵的能力。意即在符合「一定」的情境中，兒童接受使用較弱的情態詞「可能」去描繪該情境。

實驗三利用真假值實驗判斷(Truth Value Judgment Task)的實驗方式探討五歲兒童對於否定句中的情態詞的理解。實驗結果支持語義次級原則(Semantic Subset Principle)。不論句法位置的先後次序，漢語兒童皆先習得語義較強的陳述，其次才是語義較弱的陳述。縱觀三個實驗的結果，五歲兒童在不確定的情境及在理解語義較弱的情態陳述所遇到的困難可能來自同一個因素—在認知上無法處理多重可能性。換而言之，五歲兒童在認知發展上尚未能處理多重可能性，此因素阻礙了兒童在情態詞上的習得。

The purpose of the thesis is to investigate 5-year-old Mandarin-speaking children’s interpretation of modals. Using the Hidden Box Task, Experiment 1 was designed to test 5-year-old Mandarin-speaking children’s understanding of the epistemic modals yiding ‘must’ and keneng ‘might’. The results revealed that children’s performance was adult-like in the determined condition but not in the undetermined condition. Children’s difficulty in contexts of uncertainty was reflected by both positive bias and the tendency of Premature Closure. Compared with the results from Moscati and Crain (2014) and Moscati, Zhan & Zhou (2016), we suggested that the lexical size of modal expressions had impacts on learning epistemic modals. Experiment 2 investigated children’s ability to derive scalar implicature. The results revealed that 5-year-old children did not generate scalar implicature in the Hidden Box Task. They consistently accepted the weak expression keneng ‘might’ when the scenario was compatible with the strong modal yiding ‘must’.
Experiment 3 examined children’s understanding of negative sentences with the epistemic modals yinggai ‘should’ and yiding ‘must’. The findings supported the Semantic Subset Principle that children acquire the strong expressions earlier than the weak expressions, regardless of the word order. By unifying the results of the three experiments, we suggested that the difficulty in undetermined condition and interpreting the weak expression may come from the same source: the cognitive difficulty in coping with multiple possibilities. That is, the cognitive difficulty in coping with multiple possibilities hinders 5-year-old Mandarin-speaking children from demonstrating their modal competence.

Abstract i
Acknowledgements iii
Table of Contents iv
List of Tables vi
List of Figures vii
Chapter 1 Introduction 1
1.1 Modality 1
1.2 The Importance of Modality Acquisitio 7
1.3 Organization of the Thesis 8
Chapter 2 Modals in Mandarin Chinese 9
2.1 Syntactic structure of modals in Mandarin Chinese 12
2.1.1 Lin and Tang (1995) 13
2.1.2 Tsai (2010) & (2015) 15
2.2 Modality and Negation 20
Chapter 3 Acquisiton of Epistemic Modality 24
3.1 Acquisition of Epistemic Modality 24
3.1.1 Hirst and Weil (1982) 24
3.1.2 Byrnes and Duff (1989) 26
3.1.3 Noveck (1996) & (2001) 28
3.1.4 Gualmini and Moscati (2009) 32
3.1.5 Ozturk & Papafragou (2014) 34
3.1.6 Moscati and Crain (2014) 38
3.1.7 Moscati, Zhan & Zhou (2016) 43
3.2 Acquisition of epistemic modal in Mandarin 45
3.3. Summary of previous acquisition studies 47
3.4 Research Questions 51
Chapter 4 Experiments 1 & 2: The Hidden Box Task 53
4.1 Experiment 1 53
4.1.1 Methods 54
4.1.2 Results 58
4.1.3 Discussion 61
4.2 Experiment 2 63
4.2.1 Method 65
4.2.2 Results 67
4.2.3 Discussion 69
Chapter 5 Experiment 3: Modals and Negation 70
5.1 Experiment on Yinggai ‘should’ 71
5.1.1 Methods 74
5.1.2 Results 78
5.1.3 Discussion 82
5.2 Experiment on Yiding ‘must’ 83
5.2.1 Methods 85
5.2.2 Results 88
5.2.3 Discussion 92
5.3 General Discussion 92
5.3.1 Comparisons between Yinggai and Yiding 92
5.3.2 Discussion 93
Chapter 6 General Discussion and Conclusion 95
6.1 Summary of the Experimental Results 95
6.2 General Discussion 96
6.3 Some Theoretical Implications 98
6.4 Conclusion 99
References 101
Appendix A: Materials for Experiment 1 105
Appendix B: Materials for Experiment 2 109
Appendix C: Materials for Experiment 3 112

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