According to Eysenck, personality can be measured – it can be condensed into the existence of three ‘super traits’ or ‘super factors’. These are extroversion, neuroticism and he later another dimension called psychoticism.

The typical extrovert – someone who’s high in extroversion – is very outgoing, seeks the company of other people, enjoys risk-taking activities and likes sensation-seeking. By contrast, the typical introvert is rather shy and reserved, tends to prefer his or her own company, and does not seek stimulation from external factors.

Turning to neuroticism, well, the person who scores very high in neuroticism is typically someone who’s tense, edgy, highly-strung, and is preoccupied with health symptoms – with psychosomatic symptoms – and who worries excessively. By contrast, a low neurotic would be somebody who demonstrates a level of calmness, and who bounces back rather quickly from emotional upsets.

During his work at the Maudsley Hospital, Eysenck realised – he noticed that psychiatric patients had a particular type about them – they showed a kind of a coldness and a ‘detached-ness’ from society. They often found it very hard to emphasise, and they were quite aloof. And Eysenck called this personality trait psychoticism. It was later added to the personality inventory to form the EPQ: The Eysenck Personality Questionnaire. And Eysenck said actually, it’s kind of noticeable that levels of psychoticism are rather low in a healthy distribution, and so whereas other personality traits show a normal distribution in society, with people scoring at the high and the low ends of the spectrum, with psychoticism most people scored very low. So we tend to be connected members of society: showing a warmth and an empathy. What happens when people show high levels of psychoticism is that they are predisposed to some of the psychiatric disorders like schizophrenia or personality disorders. That doesn’t mean that you are likely to develop the disorder if you have high levels of psychoticism, but it means that you might be vulnerable to showing some aspects connected to those disorders.

So the EPQ was developed. The EPQ is still in use today, it comprises just over 100 ‘yes’ or ‘no’ personality questions and it also has a ‘lie scale’ to measure if people are ‘faking good’: whether they’re giving socially desirable responses.

Many years later the development of the Big Five occurred. Here we have results which are consistent to Eysenck, but which proposed the existence of two other personality traits. So this is termed the ’Big Five’. And in the ‘Big Five’ we have five key traits, and you might be able to remember these by remembering OCEAN: so we have Openness to experience; Conscientiousness; Extroversion; Agreeableness and lastly Neuroticism, which is also the same as it is in Eysenck’s measure. And so here we’re saying that personality comprises a level of openness to new experience (and you can imagine this correlates with some aspects of extroversion). Conscientiousness also has a relationship with ‘agreeableness’, so are you the sort of person who really thinks hard about his or her work; about forward planning; about getting on with tasks to hand; and how agreeable are you to other people working with you in the process of this? And extroversion and neuroticism as I’ve said are very similar to Eysenck’s key features.

This time the instrument is one which shows more of a scale-like measure rather than a ‘yes’ or no’ response, and people score in the opposites so they are either very high in openness to experience or really low in openness to experience. This is really important because the instrument has been shown to be very reliable and validated across countries so across different cultures, and if we’re to believe that personality has a biological underpinning we should see different people scoring to different levels on these five key traits.

Eysenck was the first to suggest that personality had this biological underpinning, and in terms of biology he’s suggested that extroversion is largely due to levels of cortical arousal around the brain. So people who are extroverted suffer from having very low levels of cortical arousal so in order to reach the peak level of arousal, they seek stimulation from external activities. Introverts on the other hand already have very high levels of arousal so they don’t need any extra arousal from outside activities. Turing to neuroticism, he proposed that neuroticism has a relationship to the sympathetic nervous system, so people who are highly neurotic have this kind of overactive nervous system. And psychoticism, there has been some suggestion that there are some genetic relationships in terms of psychotic behaviours / psychotic tendencies. These are largely supported with work form the Big Five, and the people who did the work on the Big Five were really dominated by two researchers who were McCray and Foster. And the scale I told you about earlier was developed by McCray and Foster and it’s called the NEO-PI.