自信，是一個重要的人格特質。人在做決策時，自信往往在無形間影響人的心理狀態，進而影響所做的決策。因此，自信程度是否越高越好，便是一項值得探討的議題。過去研究自信的文獻探討範圍僅限於個人的決策，本文將其延伸至團體的決策。研究重點即在探討團隊成員彼此互動之下，對自己的「自信」或是對團隊夥伴的「信任」程度對彼此福利所造成的影響。
    心理學對自信有多種詮釋，本文將其表現在對於自己能力的信念 (自信)，以及對團隊夥伴能力的信念 (信任)。雙方能力信念影響一個團隊在面對不確定性事件時，對成敗機率以及行動成本的評估。於是，我們藉由一個全知者 (知道真實能力) 的角度來作對照，以評斷自信的提升對整體福利究竟是好是壞。
    本文分兩種決策模式來研究自信的效果。第一個為共同決策模型，團隊成員彼此為能力信念的訊息完全狀態下共同決策；第二個為獨立決策模型，團隊成員彼此為訊息不完全狀態下獨立決策。後者係考量團隊成員在沒有其他成員能力訊息的情況下，依據自己的能力信念加以猜測。結果顯示，不論在哪一個模型，若雙方一開始的自信較為不足，則信心的提升較易產生激勵價值，有利於雙方的預期淨福利。而對夥伴的信任程度方面，研究結果顯示，不過度輕視夥伴對自信提升福利的效果是有助益的。且在模型比較中發現，若對夥伴的信任程度大於夥伴的自信程度，則獨立決策下信心提升的效果較好。總括之，在一個缺乏自信的團隊，如果彼此對夥伴採取較信任的態度，則信心的提升對雙方皆會是有利的。

Confidence is one of the important personalities. When people make decisions, confidence has virtual influence on their psychological state, and further, affects the decisions they make. Therefore, whether the higher level of confidence is better becomes an issue that is worth a discussion. While many related researches had been devoted to the personal decision making, this study leads the research to the group decision making. The aim of this report is to investigate the effect of confidence on a team’s performance and welfare, while taking into account the interactions between team members.
    Psychology interprets confidence in many ways. In this paper confidence, as reflected by the both faith, the belief in one’s own ability (self-confidence) and the belief in his partner’s ability (trust), will influence a team’s perception of success and evaluation of action costs when they undertake a risky activity. We analyze the effect of increasing confidence on activity and overall welfare.
    In this report, we develop two decision models of teamwork. One is a co-decision model, in which the team members make decisions together in the state of perfect information on the belief in ability. The other is an independent decision model, in which the team members with imperfect information make decisions simultaneously, but independently. The latter is to consider each team member making a decision based on a conjecture about his partner’s priors over his own ability. The result shows that, no matter what the model is, if initially they are both lack of confidence, the increasing of confidence will produce more motivation value which favors to both sides’ expected net welfare. As for the level you trust your partner, the result shows that not to look down on your partner will enhance the welfare effect of increasing confidence. In the comparison, we find that if the level of conjecture about your partner’s priors over ability is higher than his own belief, the effect of increasing confidence in the independent decision model will be better. To sum up, although the team is lack of confidence, if you trust your partner, the increasing of confidence will be beneficial to both sides.

目錄
目錄	I
表目錄	II
第一章  緒論	1
1.1  研究動機	1
1.2  研究目的	2
1.3  研究架構	3
第二章  文獻回顧	5
2.1  自信的概念	5
2.2  自信的來源	6
2.3  自信的價值及對決策表現的影響	7
2.4  過度自信模型	8
第三章 研究方法與模型	12
3.1 基本假設與變數設定	13
3.2 共同決策模型	14
3.2.1模型設定	15
3.2.2 均衡解	17
3.2.3 比較靜態分析	18
3.2.4 自信的效果	19
3.3 獨立決策模型	25
3.3.1 模型設定	25
3.3.2 均衡解	26
3.3.3 比較靜態分析	27
3.3.4 自信的效果	29
3.4 模型比較	36
第四章 結論	40
4.1 主要結論	40
4.2 模型延伸與未來研究方向	41
參考文獻	43
附錄	44

		
 
表目錄
表 1 自信對預期淨報酬具有正面效益的條件	36

Bandura, A. (1977). Self-efficacy: Toward a unifying theory of behavioral change. Psychological Review, 84(2), 191-215.
Bénabou, R., & Tirole, J. (2002). Self-confidence and personal motivation. Quarterly Journal of Economics, 117(3), 871-915.
Compte, O., & Postlewaite, A. (2004). Confidence-enhanced performance. American Economic Review, 94(5), 1536-1557.
Kahneman, Daniel . (2013). Thinking, fast and slow. New York:  Farrar, Straus and Giroux. 200-233.
Moore, D. A., & Healy, P. J. (2008). The trouble with overconfidence. Psychological Review, 115(2), 502-517.
O'CONNOR, M. (1989). Models of human behaviour and confidence in judgement: A review. International Journal of Forecasting, 5(2), 159-169.
Weinberg, B. A. (2009). A model of overconfidence. Pacific Economic Review, 14(4), 502-515.