Stability and validity of self-reported personality traits

Abstract

Background: People differ, and these differences are often attributed to individual differences in certain personality traits assumed to have 'more than nominal value' and to 'exist within' the individual. The aim of the present study was to evaluate some properties of a trait assessment instrument, the Karolinska Scales of Personality (KSP). More specifically, the purpose was to study the stability of the KSP scales, as well as to evaluate various aspects of validity by using prospective designs and clinical and biological correlates.

Results: Are some KSP scales more stable than others, i.e., is there a hierarchy of rank order stability coefficients for the KSP scales? In general, Socialization, Somatic and Psychic Anxiety, Muscular Tension and Inhibition of Aggression, and the scales derived from the Sjöbring model (Impulsiveness, Monotony Avoidance, Detachment and Psychasthenia), have higher stability than the Social Desirability scale and the five aggression-related scales (Indirect and Verbal Aggression, Irritability, Suspicion and Guilt). Stability would be of little interest if the scales did not also possess an ability to predict trait relevant outcomes. The ability of preoperative personality traits to predict postsurgical quality of life, was tested and the results indicated that Muscular Tension/Somatic Anxiety and poor Socialization independently predicted postoperative quality of life. Moreover, subjects who volunteered for a psychobiological study, which included a potentially painful procedure, were compared with those who declined participation. Scores on the KSP Impulsiveness scale, about 16-18 months before decision about participation, predicted subsequent volunteering.

Behavioral genetic analyses were thought to contribute to the validation of the KSP scales. In general, the most important factor explaining individual differences for all scales was the nonshared environmental component. Furthermore, results showed genetic factors to influence individual differences in scores on the Psychasthenia, Somatic Anxiety, Irritability, Guilt, Impulsiveness, Monotony Avoidance, Detachment and Social Desirability scales. Shared rearing/correlated environmental determinants were important for individual differences in scores on the Muscular Tension, Lack of Assertiveness, Psychic Anxiety, Socialization, Suspicion, Verbal and Indirect Aggression scales.

Some markers of dopamine neurotransmission have shown good biometric properties, and therefore would be appropriate targets for studies of biological correlates of the KSP scales. The allelic association previously found between dopamine D4 receptor (DRD4) genotypes and personality traits was not confirmed in this study. However, the Detachment scale showed a high correlation with [llC]raclopride, a measure of D2-receptor density, indicating an association between social withdrawal and low dopamine D2 density.

Finally, an evaluation of whether the KSP scales were differently related to objective ratings of type of personality disorder and/or to severity of personality pathology was performed. The KSP Socialization scale was found to be the scale most highly correlated with maladaptivity (severity of personality pathology). Clinical ratings of Cluster B-traits correlated positively with the Impulsiveness, Monotony Avoidance and Verbal Aggression scales and negatively with the Social Desirability scale. Three of the KSP anxiety-proneness scales were correlated with the clinically rated Cluster-C traits. In addition, both the Detachment scale and the Suspicion scale were positively correlated with the cluster C ratings, whereas Verbal Aggression manifested a negative association.

Discussion: In the discussion validity arguments are put forward focusing on coherent patterns of findings, viewing the present results in the light of previous KSP results. With the exception of some of the aggression-related scales, it is concluded that the KSP scales demonstrates stability and construct validity.