How do you measure personality?
Knowing yourself is tricky, and so is personality science.
Are you stable or thin-skinned? Anal-expulsive or anal-retentive? Are
you Type A or Type B? An ISTJ or an ENFP? Piglet, Tigger, Eeyore or
Pooh? The recent boom in personality testing has created a mindboggling
variety of options for discovering your personality 'type'.
Personality tests are used for job interviews, career guidance,
sports psychology and marriage counselling, as well as for therapeutic
and forensic purposes.
But what can they really tell us about ourselves? Personality through
history We've been trying to pin personality down since the days of the
ancient Greeks, when Hippocrates came up with the idea that four body
fluids, or humours (yellow bile, phlegm, blood and black bile), governed
our health. Based on this theory, the Greek physician Galen suggested in
200 AD that the humours influenced not only health, but our
People with an excess of yellow bile were therefore choleric (hot
tempered), those with too much phlegm were phlegmatic (calm and
unemotional), an excess of blood resulted in a sanguine personality
(optimistic and cheerful) and black bile was associated with melancholic
types (gloomy and depressed).
Sigmund Freud, working in the late 1800s and early 1900s, looked not
to our bodily fluids but our unconscious.
He linked critical stages of development like weaning, toilet
training and sexual awakening to personality, giving us a legacy of
orifice-related personalities such as 'anal' and 'oral' types.
The anal-retentive, for example, is compulsively ordered, tidy and
perfectionist; this, so the theory goes, is a result of too much
punishment during toilet training.
The testing boom
Current theories tend to categorise personality under a combination
of traits, such as introversion or extroversion, and have spawned an
entire industry based around testing (see box below).
To qualify as a factor that is useful in testing, a trait must differ
between individuals, and it must be relatively stable over time and in
Dr Miles Bore is a registered psychologist and lecturer at the
University of Newcastle who specialises in pyschometrics, or
psychological measurement, and personality assessment.
He says personality testing is driven as much by fashion as by any
inherent usefulness, although tests can be helpful in some areas, such
as choosing a career path. "There's been a lot of criticism of
personality tests and their accuracy and it waxes and wanes in the
literature," he says.
Bore says while no test is a perfect predictor of personality, they
can be a rough guide of how individuals will act in certain situations.
"If you sit a personality test, can it tell you or somebody else
exactly what you're going to do in every situation in the future? Well
the answer is clearly no," he says.
"But they can indicate the likelihood of certain behaviour in typical
A review of the big five traits in the 1999 Handbook of Personality
found that research in adolescents showed those with high
conscientiousness and openness performed better in school.
Among adults, conscientiousness was the only personality factor to
predict overall success at work, but people who scored higher on
agreeableness and neuroticism were the best performers in jobs requiring
group work, and those who scored high on extroversion did well in sales
Psychoanalyst Stephen Carroll is a skeptic. He believes personality
tests reflect the 'corporatisation of psychology' and don't prove
anything other than that a person can tick a box.
"It's bad science, it's hocus pocus, it goes to the realms of
superstition," he says. "There are people who put too much faith in
tests, who say 'I think you're a KZ9' and it's 'my god how did you
It's like saying 'you're a Capricorn'." Bond University's Professor
Greg Boyle, senior editor of the four-volume Psychology of Individual
Differences, says it's wrong to talk about personality "types" É" rather
than scores along a scale É" because personality consists of "continuous
"To call a person an introvert or an extrovert, really we're only
talking about a small percentage of people who are right at the extreme
ends of the distribution," he says.
"The vast majority of people fall somewhere in the middle." Common
personality tests Revised NEO-PI test. Developed by Paul Costa and
Robert McCrae, the revised NEO-PI test measures the so-called 'big five'
traits: neuroticism, extroversion, openness to experience, agreeableness
and conscientiousness. It is based on the five-factor model, the
dominant model of personality since the mid-1980s.
16PF test. First published in 1949 by Raymond Cattell, the 16
Personality Factor questionnaire assesses 16 traits including warmth,
dominance, privateness and perfectionism.
Myers-Briggs Type Indicator (MBTI). Designed in 1958 by Isabel Briggs
Myers and Katharine Cook Briggs, the MBTI is based on Jungian theory.
It describes people by a combination of letters based on four
dichotomies: extroversion or introversion (E or I), sensing or intuition
(S or N), thinking or feeling (T or F), and judging or perceiving (J or
P). This results in 16 different types, or four-letter code
combinations, such as an ENFP or an ISTJ.Novelty tests.
The Hundred Acre Wood personality test tells you whether you're most
like Tigger, Pooh, Piglet or Eeyore. Other novelty tests compare you to
the characters in Harry Potter, or a breed of dog.
Can you change your personality?
Professor Greg Boyle believes basic personality traits are primarily
a result of the anatomy, structure and functioning of individual brains,
although experience and learning can modify personality.
"People's brains operate differently and some people are more
extroverted depending upon the level of arousal or activation of the
brain," he says.
But this doesn't mean our personalities are fixed.
"Although personality traits are often said to be permanent fixtures
in the profile of an individual -they are not necessarily the fixed,
immutable dispositions that some people have thought.
"Personality differences show up in the brain, but brains, like
personality traits themselves, are susceptible to learning. As our
personality changes, so will the brain." Dr Doris McIlwain, a
personality psychologist at Macquarie University, says genetic studies
comparing non-identical twins living in the same environment with
identical twins living in the same environment have shown that some
aspects of our personality, like the extrovert/introvert factor, are 60
per cent due to environment.
More recently, a study by researchers from the University of Michigan
looked at the closely related (and therefore genetically similar)
population of the Mediterranean island of Sardinia.
That study, published in the journal PLoS Genetics, concluded that
genes account for only 19 per cent of documented traits like
agreeableness, conscientiousness, neuroticism and extroversion.
"My personal view is that we have evolved to have very diverse
personalities and thatÉ?›personality may be much less deterministic than
other human characteristics," says Associate Professor GonAalo Abecasis,
one of the authors.
Professor Greg Boyle says research has shown it's possible to develop
or at least change "the outward expression" of your personality.
In a study of students, published in the journal Psychological Review
in 2002, he found personality traits such as ego strength and dominance,
as measured in the Sixteen Personality Factor questionnaire (16PF), were
susceptible to learning.
Several recently published studies confirm a more fluid view of
personality, says Boyle. A 2006 review found that social dominance,
conscientiousness and emotional stability, for example, tended to
increase between 20 and 40 years of age.
Even in middle and old age, there was significant change in four out
of six personality traits, the reviewers found.
"Given that people have a very highly developed cognitive ability;
it's therefore possible for humans to consciously try to modify their
behaviour and interpersonal relations," says Boyle.