The development of the personality traits Machiavellianism, psychopathy, and narcissism is hardly understood. We theorize that the well-documented maturity principle applies to these traits. Decreasing levels of Machiavellianism, psychopathy, and the antagonistic dimension “narcissistic rivalry” could be interpreted as reflecting maturation. The self-enhancing “narcissistic admiration” trait might remain unchanged. A sample of N = 926 German university students aged 18 to 30 (74% female) participated in a longitudinal study with 4 waves of measurement over 2 years, completing short and full-length measurement instruments. The preregistered analyses included latent growth curve models based on item factor analysis with partial measurement invariance. We accounted for the possibilities of contextual effects and nonlinear development and controlled the false discovery rate. All four traits showed very high rank-order stability (rs ranged from .74 to .81). In line with the maturity principle, mean levels of Machiavellianism and psychopathy decreased linearly (ds were −0.18 and −0.12). Moreover, model comparisons revealed systematic heterogeneity in Machiavellianism’s linear growth curve, indicating that young adults differ from each other in the direction or steepness of their developmental paths. We also assessed self-esteem and life satisfaction. Linear changes in Machiavellianism were inversely related to linear changes in life satisfaction (r = −.39), making the mean-level decrease in Machiavellianism appear as adaptive. While findings concerning narcissism were inconclusive, this study provides incremental evidence that the maturity principle might apply to Machiavellianism and, potentially, to psychopathy.

A common assumption is that good leaders are driven by a power motive that motivates them to influence others. However, leaders need to restrain themselves in social dilemmas where cooperation maximizes collective outcomes. We theorize that in social dilemmas, a desire for positive relationships (affiliation motive) is more beneficial than a power motive because it draws attention away from short-term self-interest towards understanding others. In a game ofSettlers of Catanin the laboratory, we find that a functional variant of the affiliation motive relates to verbal encouragement of cooperation, to fewer occurrences of oil spills, to higher ratings of transformational leadership and, in a field survey, to fewer selfish business decisions. Furthermore, a dysfunctional variant of the power motive relates to two of three indicators of selfishness. Group members perceive selfish individuals as assuming leadership roles which indirectly relates to slightly higher ratings of transformational leadership. This pattern of evaluation may privilege men who, on average, show more selfish behaviour which can be partially attributed to their motives. Mere awareness of gender-based discrimination does not enable raters to circumvent this pattern of evaluation. This work suggests a need for interventions that increase appreciation of cooperative leaders.

In this rejoinder, we respond to two commentaries on the study by Greiff, S.; Stadler, M.; Sonnleitner, P.; Wolff, C.; Martin, R. Sometimes less is more: Comparing the validity of complex problem solving measures. Intelligence 2015, 50, 100–113. The study was the first to address the important comparison between a classical measure of complex problem solving (CPS) and the more recent multiple complex systems (MCS) approach regarding their validity. In the study, we investigated the relations between one classical microworld as the initially developed method (here, the Tailorshop) with three more recently developed multiple complex systems (MCS; here, MicroDYN, Genetics Lab, and MicroFIN) tests. We found that the MCS tests showed higher levels of convergent validity with each other than with the Tailorshop even after reasoning was controlled for, thus empirically distinguishing between the two approaches. The commentary by Kretzschmar and the commentary by Funke, Fischer, and Holt expressed several concerns with how our study was conducted, our data was analyzed, and our results were interpreted. Whereas we acknowledge and agree with some of the more general statements made in these commentaries, we respectfully disagree with others, or we consider them to be at least partially in contrast with the existing literature and the currently available empirical evidence.