Previous research on the connection between the Dark Triad traits and aggression is largely based on self-report measures. This paper examines how the traits of Machiavellianism, psychopathy and...Show morePrevious research on the connection between the Dark Triad traits and aggression is largely based on self-report measures. This paper examines how the traits of Machiavellianism, psychopathy and narcissism affect aggression in an experimental setting. Based on the previous literature, we hypothesized that Machiavellianism and psychopathy were positively correlated with aggression, while narcissism would be unrelated. We used the Attacker-Defender Conflict (AD-C), an economic contest well suited to study aggression. The incentivized AD-C was implemented in an online environment where attackers and defenders, who were matched afterwards, competed for resources. Attackers decided how much they would invest in order to beat the defender and gain money at their expense. If the defender successfully defended by investing more or an equal amount as the attacker, both parties kept their non-invested resources. Out of 301 participants, the attacker conflict investment of 132 attackers was used to measure aggression. Participants also completed the Short Dark Triad, a self-report questionnaire that evaluates Dark Triad traits. Our analysis showed a positive correlation between Machiavellianism and aggression, but only when the other two traits were held constant. Contrary to our assumption, psychopathy was negatively related to aggression. Finally, narcissism was not significantly correlated with aggression. These findings imply that, while the understanding of Machiavellianism and narcissism based on self-report measures of aggression are supported in our study, psychopathy’s connection to aggression may have either been misunderstood before or unknown factors played a significant role by confounding the results. Implications, limitations, and recommendations for future research are discussed.Show less