The Eysenck Personality Questionnaire-Revised Edition (EPQ-R) is the most recent version of the personality questionnaire designed to measure the three personality factors identified by Hans J. Eysenck (1916-1997) and others. These factors, known as psychoticism, extraversion, and neuroticism, comprise what is termed the P.E.N. Personality Model. The P.E.N. model holds that these three personality factors account for the bulk of human personality variation. That is, the model states that the personalities of humans differ primarily with respect to these three factors. Each personality factor is composed of a large number of specific traits. The EPQ-R is composed of 94 self-report items, such as "Do you like to arrive at appointments in plenty of time?" and "Do you worry a lot about your looks?" to which respondents either agree or disagree. The number of affirmative responses to items that compose each scale are summed to arrive at the scores on the three personality dimensions.
Individuals who have high scores on the Psychoticism subscale (27 items) have the potential to develop a psychotic disorder, as they may exhibit similar characteristics to those who have had a break with reality. These individuals may also have high levels of anger and are inclined to exhibit some types of conduct or behavioral disorders. They may be described as hostile or unempathic, and they may disregard societal conventions via nonconformity, recklessness, manipulation of others, and impulsivity. Other potential traits of people with high psychoticism scores include tough-mindedness, aggression, egocentrism, assertiveness, and dogmatism. Although there has been limited research on the biological basis of psychoticism, it has been suggested that these individuals have increased testosterone levels.
The Extraversion scale (22 items) measures one's level of sociability and affect. Individuals who have high scores on this subscale tend to be gregarious, carefree, and exciting. These individuals enjoy parties and feel the need to have other people with whom to talk. They are likely to be involved in social activities, and they may lose control quickly. Additional traits of people with high extroversion scores include irresponsibility, dominance, sensation seeking, and engagement in risk-taking behaviors. Individuals with low extraversion scores (a.k.a. introverts) are often characterized as reliable, somewhat pessimistic, and highly ethical. The biological correlates of extraversion include a high level of cortical arousal and general physiological arousal.
Individuals who score high on the Neuroticism scale (24 items) of the EPQ-R generally have a temperament reflective of negative affect. More specifically, they often possess high levels of anxiety and/or depression. These types of people may be frequently worried or nervous, often sleep poorly, and have high susceptibility to develop psychosomatic disorders. In addition, they may be overly emotional and react too strongly to events in their environment. Other traits that high scorers on the Neuroticism scale may have include feelings of guilt, moodiness, tenseness, obsessive thoughts, low self-esteem, and dependence. In terms of biological associations, it has been suggested that the basis for neuroticism is the sympathetic nervous system, which controls our "fight or flight" response to threatening environmental stimuli.
Self-report measures like the EPQ-R are, of course, subject to the honesty and accuracy of the respondent. Therefore, the EPQ-R also includes a "lie" scale (21 items) to detect inaccurate or socially desirable responding. If the respondent is not able to admit to a number of everyday human foibles or is trying to present him- or herself in an overly positive manner, the lie scale score will be high. When the lie scale score is high, the other scores are not interpreted.
The EPQ-R and its earlier versions have been used extensively in psychological research. That being the case, the psychometric properties of the EPQ-R have been the subject of much study. Studies of the psychometric properties of self-report questionnaires like the EPQ-R examine questions of reliability (i.e., are the scores repeatable or stable from one administration or time to the next?) and validity (i.e., do the scores really reflect levels individual differences in levels of the hypothesized construct—e.g., neuroticism— and not something else—e.g., anger?). .Although the Neu-roticism and Extraversion scales of the EPQ-R have received a substantial amount of empirical psychometric support, the Psychoticism scale has not. Specifically, scores on the Psychoticism scale have been shown to have low reliability. The construct of psychoticism has not been as ex tensively studied as neuroticism or extraversión, which may explain the psychometric weaknesses of the psychoti-cism scale.
In summary, the EPQ-R provides scores that allow for the clinical use of Hans J. Eysenck's P.E.N. model, which attempts to explain human personality variation. The EPQ-R has also been used extensively for psychological research. The extraversion and neuroticism scores have good reliability and validity for a variety of purposes. Scores on the psychoticism domain have been the focus of far less study, but even so it can be stated that they do not possess the same level of psychometric quality. The P.E.N. model is but one of many models used to explain and describe human personality, although it has enjoyed a prominent place among them. Perhaps the most important distinguishing characteristic of the P.E.N. model is the emphasis that P.E.N. supporters have placed on the biological basis of personality (see the earlier description of each personality factor). According to the leading P.E.N. researchers, personality is based in biology, and a personality factor can only be confirmed as such when biological markers or correlates are identified. This is in direct contrast to other personality models, like the Big Five Model or models based on "psychological type," where biological causes of personality are not required for the identification of a construct as a personality factor. Because P.E.N. theorists have placed this emphasis on biology, cross-species research has been more productive, even resulting in the thought-provoking notion that rats have the same three personality factors as humans!
John C. Caruso J. D. Gottlieb University of Montana
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