In the past decade, extensive interest has been directed toward the Dark Triad (i.e., Machiavellianism, narcissism, and psychopathy), popularly assessed by the Short Dark Triad (SD3). Nevertheless, relatively little research has been conducted on the SD3's factor structure. We investigated the SD3's psychometric properties in three studies with three independent samples, using exploratory and confirmatory factor analyses ( N = 1,487; N = 17,740; N = 496). In all three studies, Machiavellianism and psychopathy items displayed large general factor loadings, and narcissism larger specific factor loadings. In subsequent studies, two- and three-factor models fitted the data similarly, with the best fitting model being a bifactor model with items from Machiavellianism and psychopathy modelled as one specific factor, and narcissism as a second specific factor. On this basis, we suggest that the SD3 does not seem to capture the different mental processes theorized to underlie the similar behaviors generated by Machiavellianism and psychopathy. Additionally, we recommend the use of a single SD3 composite score, and not subscale scores, as subscales contain small amounts of reliable variance beyond the general factor.

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Background. The dark side of human character has been conceptualized in the Dark Triad Model: Machiavellianism, psychopathy, and narcissism. These three dark traits are often measured using single long instruments for each one of the traits. Nevertheless, there is a necessity of short and valid personality measures in psychological research. As an independent research group, we replicated the factor structure, convergent validity and item response for one of the most recent and widely used short measures to operationalize these malevolent traits, namely, Jonason’s Dark Triad Dirty Dozen. We aimed to expand the understanding of what the Dirty Dozen really captures because the mixed results on construct validity in previous research.Method. We used the largest sample to date to respond to the Dirty Dozen (N = 3,698). We firstly investigated the factor structure using Confirmatory Factor Analysis and an exploratory distribution analysis of the items in the Dirty Dozen. Secondly, using a sub-sample (n = 500) and correlation analyses, we investigated the Dirty Dozen dark traits convergent validity to Machiavellianism measured by the Mach-IV, psychopathy measured by Eysenck’s Personality Questionnaire Revised, narcissism using the Narcissism Personality Inventory, and both neuroticism and extraversion from the Eysenck’s questionnaire. Finally, besides these Classic Test Theory analyses, we analyzed the responses for each Dirty Dozen item using Item Response Theory (IRT).Results. The results confirmed previous findings of a bi-factor model fit: one latent core dark trait and three dark traits. All three Dirty Dozen traits had a striking bi-modal distribution, which might indicate unconcealed social undesirability with the items. The three Dirty Dozen traits did converge too, although not strongly, with the contiguous single Dark Triad scales (r between .41 and .49). The probabilities of filling out steps on the Dirty Dozen narcissism-items were much higher than on the Dirty Dozen items for Machiavellianism and psychopathy. Overall, the Dirty Dozen instrument delivered the most predictive value with persons with average and high Dark Triad traits (theta > −0.5). Moreover, the Dirty Dozen scale was better conceptualized as a combined Machiavellianism-psychopathy factor, not narcissism, and is well captured with item 4: ‘I tend to exploit others towards my own end.’Conclusion. The Dirty Dozen showed a consistent factor structure, a relatively convergent validity similar to that found in earlier studies. Narcissism measured using the Dirty Dozen, however, did not contribute with information to the core of the Dirty Dozen construct. More importantly, the results imply that the core of the Dirty Dozen scale, a manipulative and anti-social trait, can be measured by a Single Item Dirty Dark Dyad (SIDDD).

We compare how new pharmaceuticals are priced in the price-regulated Swedish market with how they are priced in the U.S. market, as studied by Lu and Comanor (1998). We collect a data set consisting of all new chemical entities (NCEs) launched in Sweden between 1987 and 1997, and test the same models as Lu and Comanor. In line with their results, we find that introductory prices depend on the degree of therapeutic innovation. Contrary to the results from the U.S. market, Swedish real prices for NCEs fall substantially over time for all classes of therapeutic innovation. Also contrary to the findings of Lu and Comanor, we find no effect of the presence of branded substitutes on either introduction prices or price dynamics. Our results indicate that the price regulation discourages price competition between brandname drugs. © 2003 President and Fellows of Harvard College and the Massachusetts Institute of Technology.