過度自信是人們依據經驗法則可能產生之謬誤判斷，人們通常會高估自己判斷之
準確性，從而導致決策之誤判，心理學上針對過度自信心理產生之原因有不同說法，
但大多認為這主要是主觀記憶、經驗法則與訊息處理有偏誤所產生之結果。經理人之
過度自信，會影響公司之價值與核心競爭能力，然而先前相關研究多專注於經理人過
度自信對公司投資、融資、併購與創新研發決策之影響，而企業之投資決策與其多角
化策略息息相關。
本研究以 2022 年 9 月最新公布之台灣 50 成分股企業為樣本，探討過度自信與企業
績效以及多角化經營與企業績效在台灣市場的表現是否與過去相關文獻相符，之後再
對多角化傾向特性是否能夠調節過度自信與企業績效的負向關係進行研究，研究期間
為 2010 至 2019 年，樣本選取排除由於性質特殊與受特別法令規範之金融、證券業等
特殊產業，另剔除財務資料缺漏不全者。
實證結果顯示過度自信與企業績效間呈現不顯著之正向影響，拒絕本文提出之假
說一。結果也顯示多角化經營與企業績效呈現顯著之正向影響，接受假說二。而過度
自信與多角化經營的調節作用呈現顯著之負向影響，故接受本文提出之假說三。

Overconfidence is a false judgment that people may make wrong decisions based on
empirical rules. People usually overestimate the accuracy of their own judgments, which leads
to misjudgments in decision-making. In psychology, there are different opinions on the
measurement of overconfidence, but most of them believe that it is mainly the result of biased
theory, rules of thumb, and information processing. Managers’ overconfidence will affect the
company’s value and firm’s competitiveness. However, previous related research focused on
the impact of managers’ overconfidence on corporate investment, financing, mergers and
acquisitions, and innovation R&D decisions. Enterprises’ investment decisions and their
diversification strategies are closely related. According to the definition of corporate
diversification by the Ministry of Economic Affairs of Taiwan: Diversification is defined as a
company having ownership of two or more industries, so “diversification” discussed in the
article adopts the classification of industrial diversification in this research. This research
attempts to use the companies in the 50 constituent stocks of Yuanta Taiwan as a sample to
explore whether the performance of overconfidence as well as diversification and firm’s
performance in Taiwan market is the same as in the past. It is studied whether diversification
can mediate the negative relationship between overconfidence and corporate performance. This
study uses the latest launched 50 constituent stocks of Yuanta Taiwan in September 2022. The
research period is from 2010 to 2019. The sample selection excludes financial and securities
industries that are special and regulated by special laws and regulations. industries, and exclude
those with incomplete financial information.

The empirical results show that there is no significant positive impact between
overconfidence and firm performance, and hypothesis 1 is rejected. The results also show that
diversification and firm performance are significantly positively correlated, accepting the
second hypothesis. The moderating effect of overconfidence and diversification also presents a
negative significant relationship, so we accept Hypothesis 3 proposed in this paper.

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