Personality psychology

is a branch of psychology that studies personality and its variation among individuals. It is a
scientific study which aims to show how people are individually different due to psychological
forces. Its areas of focus include:
  * construction of a coherent picture of the individual and their major psychological processes
  * investigation of individual psychological differences
  * investigation of human nature and psychological similarities between individuals

"Personality" is a dynamic^ and organized set of characteristics possessed by a person that
uniquely^[influences their environment, cognition, emotions, motivations, and behaviours in various
situations. The word personality originates from the Latin persona, which means "mask".

Personality also refers to the pattern of thoughts, feelings, social adjustments, and behaviours
consistently exhibited over time that strongly influences one's expectations, self-perceptions,
values, and attitudes. Personality also predicts human reactions to other people, problems, and
stress.^

The study of personality has a broad and varied history in psychology with an abundance of
theoretical traditions. Many of the ideas developed by personality theorists stem from the basic
philosophical assumptions they hold. Some of the most fundamental philosophical assumptions are the
following ones:
  * Freedom versus determinism – This is the question whether humans have control over their own
behaviour and understand the motives behind it or if their behaviour is causally determined by
forces beyond their control.
  * Heredity (Nature) versus environment (Nurture) – Personality is thought to be determined
largely either by genetics and biology, or by environment and experiences. Contemporary research
suggests that most personality traits are based on the joint influence of genetics and environment.
  * Uniqueness versus universality – This question discusses the extent of each human's
individuality (uniqueness) or similarity in nature (universality). Gordon Allport, Abraham Maslow,
and Carl Rogers were all advocates of the uniqueness of individuals. Behaviourists and cognitive
theorists, in contrast, emphasize the importance of universal principles, such as reinforcement and
self-efficacy.
  * Active versus reactive – This question explores whether humans primarily act through individual
initiative (active) or through outside stimuli. Traditional behavioural theorists typically
believed that humans are passively shaped by their environments, whereas humanistic and cognitive
theorists believe that humans are more active in their role. Most modern theorists agree that both
are important.
  * Optimistic versus pessimistic – Personality theories differ with regard to how important role
humans themselves play in the changing of their own personalities. Theories that place a great deal
of emphasis on learning are often more optimistic than those that do not.