The light side of darkness?

The duality of human nature, consisting of positive and negative personality traits, has intrigued scholars in different fields. Despite an overwhelming dominance of research on positive characteristics, particularly in the field of education, negative traits, such as those constituting the Dark Triad (DT; i.e., Psychopathy, Narcissism, and Machiavellianism) have been confirmed to be associated with both positive and detrimental outcomes. This paper aims to investigate the potential influence of these aversive traits on second language (L2) learning outcomes—L2 learning motivation, engagement, achievement, and willingness to communicate. L2 learners from a single country (n = 431) participated in this study. Multiple structural equation models (SEMs) were run to analyze the links and the directionality of significant effects. Overall, among the undesirable DT traits, Psychopathy and Narcissism were both positive and negative predictors of the L2 outcomes, while Machiavellianism unexpectedly emerged solely as a positive predictor. The intricacy of the results underscores the vague nature of the effects, pinpointing the need for more caution while examining negative personality traits in education and the L2 contexts. Based on the results of this study, implications and directions for future research on DT and language learning are suggested.