Measuring schizotypal and psychopathic traits

Schizotypal traits were assessed using the brief revised version of the Schizotypal Personality Questionnaire¹⁷ (SPQ-BR). It has 32 items which are rated on a five-point Likert scale (0 = Strongly disagree, 4 = Strongly agree), with three subscales capturing Cognitive-Perceptual, Interpersonal, and Disorganised dimensions. Psychopathic traits were assessed using the Self-Report Psychopathy Scale 4 Short Form³⁹ (SRP-4-SF). It includes 29 items and collects participant responses on a five-point Likert scale (1 = Strongly disagree, 5 = Strongly agree). The scale generates a total score for overall level of psychopathic traits and includes scores for each of the four dimensions of psychopathy: Interpersonal, Affective, Lifestyle and Antisocial. Both measures are suitable for use in the general population and are structured so that higher scores indicate more pronounced traits.

The zero-order spearman’s rank correlations between SPQ-BR and SRP-4-SF scores for Study 1 are presented in the supplementary information (Table ^S2). Correlations (r_s) ranged in size from 0.04 (SPQ-BR Interpersonal and SRP-4-SF Antisocial) to 0.44 (SPQ-BR Disorganised and SRP-4-SF Interpersonal; SPQ-BR Disorganised and SRP-4-SF Lifestyle; SPQ-BR Disorganised and SRP-4-SF Total), with all but two correlations (SPQ-BR Interpersonal and SRP-4-SF Lifestyle; SPQ-BR Interpersonal and SRP-4-SF Antisocial) reaching statistical significance.