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Chapter 14


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Ch.14 Personality
Personality – a particular pattern of behaviour and thinking prevailing across time and situations that
differentiates one person from another
- Psychologists’ assessment of personality derived from results of special tests designed to identify
particular personality characteristics
- goal is to discover causes of individual differences in behaviour
- research on human personality requires 2 kinds of effort:
oidentifying personality characteristics
odetermining variable that produce and control them
- must avoid “nominal fallacy” – false belief that causes of even are explained by simply
naming/identifying them
Personality Types and Traits
- ancient Greeks had earliest explanation for individual differences in personality
ohumoural theory - body contains yellow bile, black bile, phlegm, and blood
oYellow – bad tempered, irritable
oBlack – gloomy, pessimistic
oPhlegm – sluggish, calm
oBlood – cheerful, passionate
-Personality Types – different categories into which personality characteristics can be assigned
based on factors such as developmental experiences or physical characteristics
- people being assigned to discrete categories is rejected today by most investigators – generally
conceive individual differences in personality as being in degree, not kind
- Human reproduction reshuffles genes in each generation, making unlikely that specific set of
genes related to personality type would be passed on
- Most behavioural scientists agree personality differences relate to impact of environmental
-Personality Trait - an enduring personal characteristic that reveals itself in a particular pattern
of behaviour in a variety of situations
- People differ along a wide range of values
- Once personality traits developed, they reside in brain – if personality traits changed through
learning, those changes must have neurological basis in brain
Identification of Personality Traits
Allport’s Search for Traits
- 18 000 words from dictionary narrowed down to those that describe stable characteristics
- believed that traits were neuropsychological properties that led to behavioural consistency over
time and contexts by producing functional similarity in way a given person interprets and
experiences events

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- people with particular trait react similarly across situations b/c they experience unique sense of
similarity across those situations that guide their feelings, thoughts, and behaviour
- not all traits have equal influence on their possessors
- Cardinal traits – strong, unifying influence on person’s behaviour (rare, these people stand out –
i.e. Hitler’s oppressive power, Mandela’s commitment to justice)
- Central traits – less singular than cardinal traits but capture important characteristics of individual
(i.e. honest, warm)
- Secondary traits – characteristics that have minor influence on consistency of behaviour (i.e.
person’s tendency to frequently change jobs)
Cattell: 16 Personality Factors
- took Allport’s 18 000 words and narrowed down to 171 adjectives that made relatively complete
set of distinct surface traits (observable behaviours)
- used factor analysis to identify clusters of traits he believed to represent underlying traits
- eventually identified 16 personality factors – “source traits
Eysenck: 3 Factors
- extroversion, neuroticism, and psychoticism
- bipolar dimensions – opposites: introversion, emotional stability, self-control
-Extroversion – the tendency to seek the company of other people, to be spontaneous, and to
engage in conversations and other social behaviours with them
-Introversionthe tendency to avoid the company of other people, to be inhibited and cautious,
-Neuroticism – the tendency to be anxious, worried and full of guilt
-Emotional stability tendency to be relaxed and at peace w/oneself
-Psychoticism – tendency to be aggressive, egocentric and antisocial
-Self-Control – the tendency to be kind, considerate, and obedient of laws and rules
- Eysenck argued that most important aspects of person’s temperament determined by combo
extroversion, neuroticism, and psychoticism
- Emphasized functioning of neural system located in brain stem produces different levels of
arousal of cerebral cortex
- i.e. introverts have high levels of cortical excitation, while extroverts have low levels – need
external stimulation (interact w/others) to maintain optimum arousal level
The 5 Factor Model
-Five Factor Model – a theory stating that personality is composed of 5 primary dimensions:
neuroticism, extroversion, openness, agreeableness and conscientiousness. This theory was
developed using factor analyses of ratings of words people use to describe personality
-Neuroticism, Extraversion, and Openness Personality Inventory (NEO-PI-R)the
instrument used to measure the elements described in the 5 factor model (neuroticism,
extroversion, openness, agreeableness, and conscientiousness)
-NEO-PI-R consists of 240 items that can potentially be used to describe person being evaluated
- test items can be answered by participant or by someone he/she knows well
- i.e. “I really like most people I meet”, “She has a very active imagination” – these are rated on
scale of 1 to 5: strong disagreement to strong agreement

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- sums of answers to different sets of items represent scores on each of 5 factors
- research suggests environmental factors not as important as genetic factors for 5 Factor Model
- can be used to predict success in job performance – i.e. extroversion predict success in jobs that
require leadership (management positions)
Heritability of Personality Traits
- many studies indicate that some personality traits are strongly heritable
- can be assessed by comparing identical/fraternal twins, raised together/apart, with
biological/adoptive relatives
- studies show identical twins more similar to each other than fraternal twins – characteristics
heritable, correlation is higher (almost double)
- tested Eysenck’s factors of extroversion, neuroticism, psychoticism and found that every study
showed identical twins more similar than fraternal twins on every measure – heredity is
responsible for b/w 50 – 70% of variability in these 3 traits
- remaining 30 – 50% of variability due to differences in environment
- studies conducted to determine if family environment had significant effect on personality
characteristics – correlation in personality traits of pairs of identical twins raised together and
apart had no differences
- differences in family environment seem to account for none of the variability of personality traits
in twins studied
- people’s genetic endowment plays important role in determining how family members interact
- twins rated their family characteristics (i.e. cohesion, expressiveness, conflict, achievement,
culture, activity, etc) – identical twins agreed on ratings much more than fraternal twins
ofamily environments similar for identical twins than fraternal twins OR
ofamily environments same in all cases but simply perceived different by fraternal twins
- the first one is most likely true
- b/c in the case of hereditary differences (fraternal), one child may be more sociable – recipient of
more social interactions or treated coldly b/c disagreeable child, but identical twins have no
hereditary differences therefore amount of social interactions w/each twin is about same
- physical attributes affect child’s environment – more attractive, more favourable attention
- these studies are based on family environments within same culture
- twin studies found strong influence of family environment (but not of heredity) on belief of God,
religion, masculinity/femininity, intellectual interests – example of how personality is not
direct/indirect of person’s heredity
Brain Mechanisms in Personality
- personality dimensions of extroversion, neuroticism, and psychoticism are determined by neural
systems responsible for reinforcement, punishment, arousal
- people highly extroverted are sensitive to reinforcement
- infants who become extroverts show higher activity levels
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