Psychopathy factor 2 (erratic lifestyle & anti-sociality) weakly linked to lower intelligence; otherwise Dark Triad traits are relatively independent of IQ

Michels, M. (2022). General intelligence and the dark triad: A meta-analysis. Journal of Individual Differences, 43(1), 35-46. Jan 2022. http://dx.doi.org/10.1027/1614-0001/a000352

Abstract: The dark triad of personality (D3) – consisting of psychopathy, Machiavellianism, and narcissism – is a set of socially aversive personality traits. All three traits encompass disagreeable behavior and a particular disregard for the well-being of others, but also a tendency to strategic and deceptive manipulation of social environments in order to attain one′s goals. To exercise these complex manipulations effectively it seems beneficial to have high cognitive abilities. Therefore, a meta-analysis was conducted to examine possible relationships between intelligence and the dark triad. A total of 143 studies were identified to estimate the strength of relationships between the D3 and general, verbal, and nonverbal intelligence. The results indicate that none of the constructs of the dark triad are meaningfully related to intelligence. However, there was a small negative correlation between intelligence and Factor 2 psychopathy. The substantial heterogeneity regarding the observed effect sizes could not be explained with meta-regression for the most part. There was no evidence for a publication bias. In total, the results challenge the notion that the dark triad is an adaptive set of personality traits that enables individuals to effectively manipulate their social surroundings.

Keywords: intelligence, psychopathy, Machiavellianism, narcissism, meta-analysis

Discussion

The meta-analysis showed that the D3 and intelligence are at most weakly related. Whereas the psychopathy-intelligence-relation is negative, for M and N there seems to be no relation at all. It should be noted that the study sample for M and N is considerably lower compared to P. Two of three expectations were corroborated. Whereas M and N were (as expected) not related to cognitive abilities, the relation between psychopathy and intelligence was significant but very small. The cause for the effect might be the overlap between P and criminality: the latter has shown to be negatively related to intelligence. This becomes particularly evident considering the small negative relation between intelligence and the P-Factor 2 (the aspect of psychopathy that comprises norm-violating behavior). Since criminality is part of many P-test-items, it would be inadequate to interpret this overlap as confounding. Furthermore, intelligence is negatively related to impulsivity (Schweizer, 2002; Vigil-Coleṭ & Morales-Vives, 2005) and aggression (Ackerman & Heggestad, 1997) – two conceptual features of Factor 2 psychopathy. Alternatively, the negative P-intelligence-relation might be due to range restriction in the primary studies and might disappear in the course of a secondary analysis of all raw data – yet the analysis of raw data mentioned above suggests the opposite. Nevertheless, the results indicate that D3-individuals do not have superior cognitive abilities that might enable them to show complex manipulative behavior. On the other hand, they do not seem to have relevant cognitive deficits as well. If one assumes that D3-individuals can indeed be more successful in some contexts than others (an assumption that should be scrutinized in the first place), this analysis demonstrates that this possible success is not a consequence of high cognitive abilities.

Surprisingly, the reanalysis of the raw data showed a moderate negative relation with intelligence: it is unclear if the study sample coincidently showed a moderate effect or if the meta-analytic results might have to be reinterpreted. A reanalysis of the original data from the primary studies might have shown similar results due to an underestimation of effect sizes due to range restriction in the isolated studies. But note that an overestimation of the effect in this meta-analysis is also possible due to range restriction. On the other hand, for example, Watts et al. (2016) found similar results as in this meta-analysis regarding P-intelligence and did correct for range restriction using a formula for correcting correlation estimates by Hunter and Schmidt (1990), which did not alter their overall results. However, the results from a P-gI-meta-analysis with k > 100 might be more credible than the reanalysis of only 7 datasets. The reanalysis of raw data did not raise any reason to further inspect the D3-relations to intelligence in regards to non-linear relationships.

Limitations of the Meta-Analysis

A few limitations of this meta-analysis should be considered: First, the combined effect sizes remained heterogeneous even after moderators had been taken into account. As a result, the reported overall effects may be quite different in subpopulations not under investigation in the present study. Second, the number of studies for M and N was very small, so that the inference had to be restricted to the types of studies under investigation and cannot be further generalized due to the use of the FE model. Third, the selection of tests for M and N that were used in the primary studies was narrow – which also made possible subscale-analyses for M and N impossible. This does not apply for P and most of the studies used the PCL (which is considered the “gold standard”-measure for psychopathy). Forth, a more fine-grained analysis of intelligence subdimensions on the basis of an overarching model of intelligence – preferably the Cattell-Horn-Carroll theory (Carroll, 1993) – would have been desirable. Since the number of effect sizes per effect-size-category (e.g., P-gI) would have dropped substantially, a rather rough separation into verbal and non-verbal was the pragmatic consequence. Lastly, no gray literature was included in this analysis: Since there was no specific search for unpublished studies on the research question, a substantial body of literature might have been missed – nevertheless, the gray studies that were identified did not differ in methodology nor the reported effect size. Consequently, there was no reason to include them.