LAUSR

Introduction The Dark Triad is a term used to describe a constellation of three socially undesirable personality traits: narcissism, psychopathy, and Machiavellianism. Contrary to Altruism (the desire to help others with no personal reward or gain), these traits are harmful to others. Given the increased scientific interest on the dark triad, Jonason and Webster developed a shorter questionnaire to evaluate these three independent-yet-related constructs with only 12 items – Dirty Dozen (D12). Objective To investigate the psychometric properties of the Portuguese version of the Dirty Dozen. Methods A community sample composed of 286 university students (69.2% females; mean age = 21.09 ± 2.133; range: 17–33) answered the Portuguese preliminary versions of the Dirty Dozen and of the Altruism dimension from HEXACO-100. To study the temporal stability, 30 participants (66.7% females) answered the D12 again after six weeks. Results The EA Cronbach alpha was “very good” (a = 0.72). Following Kaiser and Cattel Scree Plot criteria, three meaningful factors were extracted which explained variance (EV) was of 54.64%: F1 Machiavellianism (EV 32.07%; a = 0.73), F2 Narcissism (13.665%; a = 0.74), F3 Psychopathy (8.90%; a = 0.64). The test-retest correlation coefficients were high, positive and significant for the total D12 and its dimensions (r > 0.70; P < 0.001). Pearson correlations of D12 total and dimensional scores and Altruism were negative, moderate and significant (r@ − 0.30). Conclusions The Portuguese version of Dirty Dozen has good reliability and validity. It could be very useful both in clinical and research contexts, namely in an ongoing project on the relationship between dark triad and perfectionism traits. Disclosure of interest The authors have not supplied their declaration of competing interest.