ABSTRACT
Several converging lines of research now strongly indicate that the psychotic states, especially schizophrenia, have associated with them personality and other characteristics which can be observed in normal individuals and which almost certainly help to define the predisposing features of such disorders. The recently developed Eysenck P-scales - both adult and junior versions - purport to tap such characteristics and therefore to provide a questionnaire instrument for measuring the third dimension of psychoticism which Eysenck’s personality theory has always contained. In reviewing the current status of the adult P-scale a number of problems with the validity of the new questionnaire are noted. These include the failure of the ‘criterion groups’ of diagnosed psychotics to achieve particularly high scores on the scale, the intrusion of Lie scale responding on P-scale performance, and the questionable face validity of the latest version of the scale (the EPQ), the items of which focus more on general anti-social traits than on obviously psychotic characteristics. Doubts are also raised about the feasibility of capturing within a single scale the characteristics associated with all forms of psychotic disorder. Despite such reservations, it is concluded that the Eysenck scale probably does tap part of the variance of psychotic traits to be seen in normal people. This is illustrated by reference to work on “psychoticism” carried out by the author and his colleagues. Historically, that work started from a slightly different viewpoint, attempting to isolate psychophysiological characteristics in psychotic patients and then searching for evidence of these in normal people. Appearance of the P-scale caused a convergence with Eysenck’s work and several experiments reported here help, in the author’s view, to strengthen the validity of his questionnaire. Thus, high P scorers have been found to resemble psychotic patients in a number of psychophysiological characteristics and to behave in a way which is consistent with the author’s theory that schizophrenia involves a curious form of central nervous “imbalance.” Recent observations suggest, however, that this resemblance may be confined to certain high P scorers, namely introverts; the finding confirms an unsatisfactory feature of the scale—the heterogeneity of groups scoring highly on it—but at the same time suggests that when used in combination with other personality measures the P-scale may be capable of identifying at least some individuals predisposed to particular forms of psychosis. Pursuing the latter line of reasoning, further work in the author’s laboratory is now attempting to develop a “borderline schizophrenia” questionnaire, judged to have better face validity than the P-scale, but intended to be used alongside it in future psychological and psychophysiological studies. Results so far look promising, especially some findings relating the new questionnaire to hemisphere differences in information processing. It is concluded that the concept of dimensionality as applied to the psychotic states is eminently viable and that, although many problems of theory and measurement remain, Eysenck can, on both counts, be considered a major pioneer in the field.
