The psychology of individual differences examines how people’s personalities differ, along with their thoughts and feelings. It is the study of how people differ and why people differ. It poses the question as to why two genetically identical twins raised in the same environment can have contrasting ways of dealing with the world, or personalities. This field integrates methodology and other subject matter along with examining a wide range of factors such as personality, intelligence, memory, ability, IQ, interests and values. Yet there is no agreed way to look at individual differences. Trait theoriesThe trait theory is lens through which individual differences are examined. The trait theory uses factor analysis to discover the main ways in which people differ from each other and designs tests to measure these traits. It also checks whether people’s traits are consistent. Trait theories are considered to be the most widely used way to study personality, which trait theory is the best one is still to be decided however. One reason why people study traits is to describe how someone will act most of the time. Unfortunately Psychobiological approachSocial cognitive approach Psychodynamic approach:In Psychology a psychodynamic theory is a view that explains personality in terms of conscious and unconscious forces. Psychodynamic theories commonly hold that childhood experiences shape personality. These theories involve psychoanalysis, a therapy that attempts to reveal unconscious thoughts and desires. Sigmund Freud proposed a psychodynamic theory stating personality consists of the Id, superego and the ego. HumanistThe humanist approach towards individual differences is relatively new in comparison to other fields of psychology and has been criticized for it’s lack of empirical evidence. However, this approach has some insightful hypotheses. Maslow’s hierarchy of needs lends the idea that individual differences in interactions with the world may stem from how one’s needs are met or not met. Similarly, Roger’s self concept proposition posits that individual differences may stem from a persons self- concept and discrepancies between the actual self and the ideal self. Hence, the humanist theory incorporates a situational approach to personality that other theories fail to do. Assessing personality Assessing individual differences is limited by the subjective nature of personality, the inconsistency of people across contexts, and by the validity and reliability of personality tests.