Freud believed there were five psychosexual stages that people went through as they matured into adults. Either frustration and overindulgence in a particular stage might lead a person to become fixated in that stage. The oral stage is the first stage that a person goes through, and is very mouth-oriented. A person in this stage will have a tendency to bite, suck, swallow, and generally explore the world with their mouth. The oral stage is typically experienced for the first year of life, during which infants are frequently seen to place unnatural objects like sand or plastic in their mouths.

Stagnation or fixation in the oral phase could lead these effects to linger into adulthood. The compulsion to chew metal or other items, as is common in pica, could be attributed to this phenomenon.

The big five personality traits are openness, conscientiousness, extraversion, agreeableness, and neuroticism. Use the acronym OCEAN to help you remember.

The five stages of Freud's psychosexual development are: oral, anal, phallic, latent, and genital. At each of these stages, he theorized that one could become "fixated" and thus have consequences on personality throughout the lifetime.

Though there are numerous feminist criticisms of the idea of penis envy, the main argument is that Freud's concept is an abstract idea built on the premise that women subconsciously want to be men, implying it is better to be a man. If there were such a thing as "penis envy," feminists suggest it would be due to men's advantages in society due to perceptions engrained in social contexts.

Freud believed that the ego helps us deal with life's demands (reality), whereas the superego deals with cultural rules, and the id operates on the pleasure principle. 

According to the theory, mesomorphs are muscular and mature-looking, have a sense of adventure and courage, and desire to dominate and have power. The other two types are ectomorph, which are thin and young-looking people who are self-conscious and introverted, and endomorphs, which are round people who are tolerant and sociable and have over-active digestive systems. The connection of temperament and character with the physical types has been widely discredited.

In Rogers' theory, individuals strive for congruence, or rather, a match between their imagined self and reality. When this match is not achieved, we describe the disconnect as incongruence. Possible selves are the cognitive concept of an individual's goals, hopes, or anxieties about their future. For example, a teenager's possible selves might include being a mother or a doctor, but might also include being an addict or homeless.

An adaptation of Gardner's ideas of interpersonal and intrapersonal intelligence, EQ was brought forth by Daniel Goleman as an alternative to traditional IQ for indicating which people tend to be more successful in life.

Prior to Erik Erikson, most theorists held that development ended in adolescence or early adulthood, after that, they argued, personality was essentially stable. Erikson argued that adults of all ages continued to face new challenges that shape their personalities as they age. Erikson's conception of development across the lifespan is unique and has continued to influence modern personality theorists and humanistic psychotherapists long after his death. 

The idiographic view supports that people are highly unique in their personalities and psychological structure to the point where they can't be compared to other people. Those who conduct research in support of this view often use case studies as opposed to general surveys.