This chapter presents the most salient psychological theories of personality. Personality is a core determinant of individual differences in everyday behaviors. The chapter discusses the difference between what psychologists broadly refer to as normal and what they regard as abnormal or clinical/mental illness. If one looks for an Elvis among personality psychologists, Sigmund Freud would be the one. During the mid-20th century, behaviorism emerged as a dominant paradigm for understanding human behavior, including personality. Although the social cognitive theory of personality has its origins in the radical behaviorist tradition, it emerged in clear opposition to it. According to the lexical hypothesis, historically, the most important and socially relevant behaviors that people display will eventually become encoded into language. Indeed, personality disorders are defined as long-standing, pervasive, and inflexible patterns of behavior and inner experience that deviate from the expectations of a person’s culture.

This chapter suggests some new directions that personality research is, or should be, taking as well as the future agenda of this research. In contrast, personality psychology provides us with a solid evidence base that people can lean on when searching for answers about human nature. Personality refers to the stable and consistent patterns we observe in how people behave, feel, and think. Associations between personality and intelligence have been found on the measurement level and hypothesized at a conceptual level. It is supposedly human nature not to trust humankind to provide the unselfish responses in questionnaires, or to possess an adequate level of self-awareness. Admittedly, this trend has been changing. An increasing number of organizations are using self-report personality measures and even laypeople seem to accept the notion of questionnaires more kindly than before.

This chapter discusses the effects of personality with respect to the other, that of getting ahead. The literature examining the impact of personality on career-related outcomes is vast and stretches back to the beginnings of psychology. The chapter reviews the most important research and paradigms concerning the areas of: academic achievement, work performance, leadership and entrepreneurship. Early reviews of the relationship between personality and job performance seemed to suggest that personality was a trivial or insignificant predictor of job performance. Psychological theories focusing on leaders’ personality or traits were influenced by Carlyle’s ‘Great Man‘ theory of leadership, which posited that ‘the history of the world was the biography of great men’. Over the past 20 years, an increasing amount of attention has been given to the area of bad leadership. The literature on personality and leadership suggests that a leader’s personality has a substantial influence on how the group performs.