Personality is the relatively consistent patterns of thought, feeling and behaviour that characterize each person as a unique individual. A trait is a relatively stable predisposition to behave in a certain way. There are traits that are always present, but there are also traits that need a certain situation before they manifest. Traits are dimensions, which are measurable, continuous characteristics, along which people differ by degree.

Trait theories of personality endeavour to specify a manageable set of distinct personality dimensions that can be used to summarize the fundamental psychological differences among individuals. Factor analysis is used in defining the most useful dimensions. There are three steps in factor analysis:

1. Collect data from a lot of people
2. Factor extraction
   Correlate the data with each other. Here you correlate the terms with each other (e.g: friendly and likeable).
3. Label
   Here the factors that correlate strongly together get a new label, such as conscientiousness.

Factor analysis tells us that the dimensions are relatively independent of each other. The Big Five Theory of Personality states that someone’s personality is best described using five, relatively independent personality dimensions. These dimensions spell out OCEAN.

1. Neuroticism – Stability
2. Extraversion – Introversion
3. Openness to new experience – Non-openness
4. Agreeableness – Antagonism
5. Conscientiousness – Undirectedness

There was a proposal for a higher-order personality trait independent of IQ that is predictive of success in a wide range of domains and is called grit. Grit is defined as perseverance and passion for long-term goals. Especially the tendency to persist at difficult tasks seems to be important for predicting success. The validity of the Big Five Theory of Personality is measured by checking the correlation between the test and the actual behaviour.

People with socially aversive personalities score high on the dark triad, which consists of three things:

1. Narcissism
   Extreme selfishness with a grandiose view of one’s abilities and a need for admiration
2. Machiavellianism
   Predisposed to manipulate other people, often through deception.
3. Psychopathy
   Amoral or antisocial behaviour, coupled with a lack of empathy and an inability to form meaningful personal relationships.

Personality is relatively constant throughout adulthood and stays constant after 50 years of age. The older someone is, the less likely it is that their personality is going to change. The heritability of personality traits is about 0.50. The household in which an individual grew up does not correlate with personality at all. A single gene may influence neuroticism, as well as the neurotransmitter serotine. A single gene may influence novelty seeking, as well as the neurotransmitter dopamine.

It could be that personality is a side-effect of evolution. It could also be that personality has an evolutionary advantage. If there are more different types of individuals in one species, the likeliness of survival is bigger. There are differences in behavioural styles across species. The Big Five can be thought of as alternative general strategies for solving problems related to survival and reproduction. There is a trait that is associated with change and is called differential susceptibility to environmental influence. Individuals with this trait are very susceptible to their environment, for better and for worse.

Pre-existing small differences between siblings may become exaggerated in part because siblings tend to define themselves as different from one another and tend to accentuate those differences through their own behavioural choices. The sibling contrast refers to the within-family emphasis on the differences between siblings. The split-parent identification is a tendency for each of two siblings to identify with a different one of their two parents. A possible explanation for why siblings and parents accentuate differences is that is could possibly reduce sibling rivalry, which can be disruptive to family functioning.

There are gender differences in personality. Women score higher on agreeableness than men and women generally score higher on neuroticism. Gender influences the personality one develops. A possible explanation for this lies in cultural expectations for each gender. Gender differences in personality can be explained by the social expectations for each gender.

Freud used the term psychoanalysis to refer both to his method of treatment and to his theory of personality. Today, the type of therapy Freud used is called psychodynamic theories. These theories emphasize the interplay of mental forces. People are often unconscious of their motives and there are processes called defence mechanisms within the mind to keep unacceptable or anxiety/producing motives and thoughts out of the consciousness. Freud proposed a theory in which a child develops through several stages:

1. Oral stage (birth to 1 year)
   Sexual excitation is centred around the mouth.
2. Anal stage (1 to 3 years)
   Anal needs become increasingly important.
3. Phallic stage (3 to 5 years)
   Resolution of the Oedipus and Electra complex.
4. Latency stage (5 years to the beginning of puberty)
   No body parts arouse sexual pleasure
5. Genital stage (adolescence and adulthood)

Erikson believes that there are several psychosocial stages of development:

1. Basic trust versus mistrust (birth to 1 year)
2. Autonomy versus shame and doubt (1 to 3 years)
3. Initiative versus guilt (3 to 6 years)
4. Industry versus inferiority (6 years to puberty)
5. Identity versus identity confusion (12 to 18 years)
6. Intimacy versus isolation (young adulthood)
7. Generativity versus stagnation (middle adulthood)
8. Integrity versus despair (late adulthood)

Freud believes that the real reason for our actions lies in the unconsciousness. Defence mechanisms are mental processes of self-deception with the goal to reduce one’s consciousness of wishes, memories and other thoughts that would threaten one’s self-esteem or in other ways provoke a strong sense of insecurity or anxiety. There are several defence mechanisms:

1. Repression
   Anxiety-producing thoughts are pushed out or kept out of one’s consciousness.
2. Displacement
   The unacceptable wish is redirected toward a more acceptable alternative.
3. Sublimation
   This is a displacement in which a person’s wish is directed toward activities that are particularly valued by society.
4. Reaction formation
   Forming a different reaction for the true emotion (e.g: a hatred towards your mother may be changed in intense love towards your mother).
5. Projection
   Projecting a characteristic or attribute onto someone else.
6. Rationalization
   The use of conscious reasoning to explain away anxiety-producing thoughts or feelings.

Repressors are people who regularly repress emotions accompanying disturbing events in life. Repressors report less psychological distress but show more physiological distress than non-repressors. Defence mechanisms can be divided into three separate categories:

1. Immature defence mechanisms
   These are the defence mechanisms that distort reality the most and lead to the most ineffective actions (e.g: projection).
2. Intermediate defence mechanisms
   These are the defence mechanisms that lead to less distortion of reality and are more effective ways of coping (e.g: repression and reaction forming).
3. Mature defence mechanisms
   These are the defence mechanisms that lead to the least distortion of reality and lead to the most adaptive behaviours (e.g: suppression and humour).

Humanistic theories of personality emphasize people’s understanding of themselves and their capacity to choose their own paths to fulfilment. Phenomenology is the study of conscious perceptions and understandings. Phenomenological reality refers to each person’s conscious understanding of his own world. Self-actualisation refers to the process of becoming one’s full self. This includes realizing one’s dreams and capabilities. People will always make choices that are best for their own development. According to phenomenologists, humans have five needs that are in hierarchical order:

1. Self-actualisation needs
2. Esteem needs
3. Attachment needs
4. Safety needs
5. Physiological needs

People can only focus on a higher need if the one below it is sufficiently satisfied.

Social-cognitive theories of personality emphasize the roles of general beliefs about the nature of the world, which are acquired through one’s experiences in the social environment. The locus of control refers to the tendency of people to behave according to a generalized disposition (a personality trait) acquired from past experience. People who believe that they control their own rewards are said to have an internal locus of control and people that believe that rewards are controlled by factors outside themselves are said to have an external locus of control.

Self-efficacy refers to people’s beliefs about their own abilities to perform specific tasks. Self-efficacy refers to the person’s sense of his own ability, while the locus of control refers to the person’s belief that ability will produce its desired effects. If people expect that they can do something, they are more likely to be able to do it. People who are more malleable, meaning that the belief that they are not fixed entities are more likely to strive for self-improvement.

The personality traits of the big five can differ per situation. Two children can have the same score for aggression, but that trait might manifest itself in completely different situations for both children (e.g: one child shows aggression when warned by an adult while another child shows aggression when teased by a peer).

The eight DIAMONDS dimensions of situations measure the situations. It describes the situation.

1. Duty
   Does something need to be done?
2. Intellect
   Is deep information processing needed?
3. Adversity
   Is someone being threatened?
4. Mating
   Does the situation involve sexual or romantic content?
5. Positivity
   Is the situation positive?
6. Negativity
   Do negative things taint the situation?
7. Deceptions
   Is someone being deceptive?
8. Sociability
   Does the situation involve social interaction and possible relationship formation?

There are cultural differences of personality, especially across collectivistic and individualistic cultures.