What Does the P Scale Measure?

¹ Psychology Department, City of London Polytechnic, School of Science and Technology, 31 Jewry Street, London, E.C.3

This study was conducted to investigate the validity of the questionnaire scale of Psychoticism, since the arguments for constructing the scale appear to be rather questionable and the data in support of the scale unsatisfactory. One hundred and three patients in a hospital for abnormal offenders were tested with Eysenck's P, N, E and L scales as well as with personality scales derived mainly from the MMPI. The results indicate that: (1) P is rather unreliable; (2) the items of the P scale do not consistently mark a factor separate from neuroticism and extraversion; (3) only 5 items meet the criteria for use as a scale; and (4) the P scale is found to be a good measure of the factor generally called Emotionality. A comparison of 18 psychotics with 18 non-psychotic offenders, matched individually for intelligence, resulted in no differences on P. Theoretically, it is argued that the concept of psychoticism as a personality dimension is based on unjustified assumptions. On the basis of the present results and previous research it is concluded that the evidence falsifies the hypothesis that the P scale is a measure of a dimension of psychoticism, but that it might be construed as a measure of a broad semantic dimension of evaluation.