Identical twins reared together tend to be about as similar in their personality traits as identical twins reared apart.
Environmental factors shared among members of the same family play an important role in the causes of most personality traits in adulthood.
Birth order is weakly related to most personality traits.
Freud believed that sex was the only important drive in personality.
Freudians would say that most persons with very high opinions of themselves have overdeveloped egos.
According to Freudians, a given dream symbol (such as a snake) does not have the same underlying meaning for every dreamer.
According to Freud, a person who is orally fixated would be likely to drink excessively.
One strength of Freudian theory is that many of its predictions are hard to disprove.
Most neo-Freudian therapists, such as Adler, placed less emphasis on social influences on personality development than did Freud.
For radical behaviourists, our personalities are bundles of habits influenced by learning.
Radical behaviourists argue that we are sometimes 'unconscious' of the true causes of our behaviour.
Social learning theorists believe that observational learning is a key form of learning in addition to classical and operant conditioning.
According to social learning theorists, individuals with an internal locus of control are more prone to depression than individuals with an external locus of control.
According to Rogers, human nature is inherently positive.
Rogers believed that only severely disturbed people aquire conditions of worth.
Maslow claimed that almost all self-actualised individuals are sociable and easy to get along with.
Many claims of humanistic models are difficult to test.
One limitation of the big five model is that researchers have identified these traits only in American culture.
Research demonstrates that after late childhood, the levels of most personality traits virtually never change over the life span.
Personality traits typically predict behaviour in a single situation with high levels of accuracy.
According to Eysenck, extraverts tend to be less aroused than introverts.
Items with low face validity tend to be especially easy for respondents to fake.
Simple formulas that can be programmed into computers yeild MMPI-2 interpretations equal or superior to those of experienced clinicians.
Adding the Rorschach Inkblot Test to other measures in a test battery sometimes produces significant decreases in validity.
The more detailed and specific an astrological horoscope is about someone's personality traits, the more likely that person will perceive it as accurate.
Researchers suggest that although students sometimes fall victim to illusory correlation, experienced clinicians do not.
