This paper discusses the limitations of achievement tests in measuring soft skills, which are personality traits, goals, motivations, and preferences that are crucial in various domains. Achievement tests often fail to capture these important skills, which, however, significantly predict success in life. The paper highlights that soft skills causally produce success and that interventions enhancing these skills can have a substantial impact on public policies. It reviews evidence from psychology and economics, focusing on two examples: the General Educational Development (GED) test and the Perry Preschool Program. The GED test, despite being an alternative to a high school diploma, does not adequately measure personality traits, leading to poor outcomes in the labor market. In contrast, the Perry Preschool Program, which focused on improving personality traits through early childhood interventions, had lasting positive effects on children's lives, even though it did not permanently change their IQ scores. The paper emphasizes the importance of considering soft skills in educational and policy contexts to better predict and promote success.This paper discusses the limitations of achievement tests in measuring soft skills, which are personality traits, goals, motivations, and preferences that are crucial in various domains. Achievement tests often fail to capture these important skills, which, however, significantly predict success in life. The paper highlights that soft skills causally produce success and that interventions enhancing these skills can have a substantial impact on public policies. It reviews evidence from psychology and economics, focusing on two examples: the General Educational Development (GED) test and the Perry Preschool Program. The GED test, despite being an alternative to a high school diploma, does not adequately measure personality traits, leading to poor outcomes in the labor market. In contrast, the Perry Preschool Program, which focused on improving personality traits through early childhood interventions, had lasting positive effects on children's lives, even though it did not permanently change their IQ scores. The paper emphasizes the importance of considering soft skills in educational and policy contexts to better predict and promote success.