In this book, Nettle begins with an overview of how the "Big Five" (extraversion, neuroticism, conscientiousness, agreeableness, openness to experience) have been determined and describes how people who behave differently have different characteristics. One of the main points Nettle makes is the difference between the characteristics that differentiate one human being from another. It also highlights the theory of how these traits evolve over time. What particularly interests me is the question of why population? Why aren't we all pretty much the same? According to Nettle, the answer is that there is no single optimal personality that is always beneficial to have. The core of the book is made up of five chapters that explore each trait of the “Big Five.” Each term is described in how it relates to the brain mechanism or function it expresses. For example, people who are characterized by high extroversion are generally energetic and enjoy being social. Professors, politicians, and entrepreneurs are all considered extroverted people. On the other hand, neurotic people tend to experience feelings such as guilt, panic, anger, sadness, and sometimes depression. Nettle also defines conscience as the state of being complete, careful, or cautious. This trait also involves the desire to strive for perfection in completing tasks. Agreeableness refers to individuals whose concerns are associated with cooperation and social harmony. These people are often identified as friendly, caring, generous, and kind when it comes to interacting with others. Finally, openness to experience applies to the willingness to explore new adventures, as well as the search for new challenges. People who are highly open to experience......middle of article......influences include learned responses, unconscious thought processes, expectations and interpretation, sociocultural influences are made up of childhood experiences, of the child's influence. situation, cultural expectations and social support. Again, this ties back to Freud's theory of a developing personality, stating that there are several components and influences that help shape a person's unique personality. In the final chapter of the book, Nettle explains that if these traits are constantly applied to our lives, we are capable of changing our lives more than we can imagine. However, many changes occur throughout life. As we grow and mature, conscientiousness and agreeableness tend to increase within our personality, while neuroticism, openness, and extroversion decrease. This reflects changes from the desire to achieve goals to relationships with others..