Unlike previous studies of overconfidence bias that have been looking for causes of overconfidence bias in human cognitive error or in the desire to view oneself positively, this study presents the cognitive narrowing resulting from the social exclusion experience as the condition of overconfidence bias. It seeks to examine what are the characteristics of cognitive narrowing, which is one of the strategies for overcoming the negative emotions resulting from social exclusion, and how cognitive errors called overconfidence bias occur due to cognitive narrowing. The present study was performed with 94 college students in Seoul. Participants were randomly assigned to a group who experienced social exclusion and a group who did not experience social exclusion. We analyzed how the degree of bias of overconfidence differs according to the experience of social exclusion by t-test. The degree of overconfidence bias of the group who experienced social exclusion was higher than that of the group who did not experience social exclusion, and the difference was statistically significant. This study extends the concepts of escaping theory and cognitive narrowing to human cognitive bias and confirmed that social exclusion experience increased cognitive narrowing and overconfidence bias. Implications and future research directions were discussed.

The study aims to investigate the existence of overconfidence bias in Vietnam, Thailand, and Singapore. This paper focuses on the Vietnam Stock Market and other two countries of ASEAN, namely Singapore and Thailand. Data was collected over the period from January 1, 2014 to December 31, 2018, daily returns for each of the securities. This paper uses the time series method, namely ADF test, Granger Causality and VAR approach to find evidences of the overconfidence effect in Vietnam in relation to some ASEAN markets. The results show similarities between the observed countries with slight variations, with focus on Vietnam market. In general concrete evidences of overconfidence were found in both Vietnamese and Singaporean markets, in which Singaporean investors show higher degree of overconfidence than Vietnamese investors. Overconfidence is not as clear in Thai market, however a direct causal link from increased returns to increased investor confidence was found. From the model deployed in the paper, there are reasons to conclude that Thai investors are under-confident. The findings of the study shed lights into the existence of overconfidence bias in Vietnam, Thailand, and Singapore on a comparative basis, provide more insights and implications for future research in this new and rising field of research.