Behavioral Factors Influencing the Investment Private Investor’s Investment Decisions in The Vietnamese Stock Market ____________________________________________________________________ Le Thai Nhat, To Hoang Lan, Nguyen Hoang My Ngoc, Luong Thi Phuc Hung, Le Thi Phuong Thao Research Summary – Abstract Individual investment in the stock market and investment decision-making behavior are closely linked. Taking advantage of the limitations of the existing literature, this article investigates the relationship between investment decisions using quantification and causality. Behavioral finance research looks at how psychological and behavioral factors influence financial decision-making. The available literature shows that individuals often exhibit biases, such as overconfidence and fear of loss, which can lead to suboptimal investment decisions. In addition, social and cultural factors, such as peer pressure and herd behavior, can also influence financial choices. Studies have also determined that individuals tend to make decisions based on emotion rather than rational analysis, which can lead to financial losses. Furthermore, research has shown that individual behavior can influence the broader financial markets, creating feedback loops and amplifying market volatility. The findings of behavioral finance research can inform policymakers and investors on how to improve financial decision-making and reduce potential risks in the markets. Using argumentative theories from existing studies, structure the report and argument based on theory and data. In addition, using data analysis tools and designing questionnaires based on the main topic and prerequisite questions set forth to find out the answers to this research paper, thereby making The most objective assessment based on data and summarizing makes a judgment of the analyzed data and compared with previous research papers.