Research published in Personality & Individual Differences shows that narcissism is linked to higher fertility, while traits like psychopathy and Machiavellianism, mediated by criminal behavior, reduce reproductive success.
Janko Međedović examined the intersection of the Dark Tetrad traits—psychopathy, narcissism, Machiavellianism, and sadism—with reproductive fitness in a criminal population. These traits, known for their socially aversive characteristics, often lead to behaviors such as manipulation and norm violations. Prior studies have highlighted inconsistent links between these traits and fertility, with some suggesting psychopathy and narcissism may enhance reproductive success in certain contexts. However, these findings are limited and often contradictory, necessitating further investigation.
Previous research on criminal behavior and fertility has also yielded mixed outcomes, with some findings suggesting a “fast life history” trajectory while others demonstrate reduced fertility due to lifestyle factors such as substance abuse and underemployment.
This study was conducted in five major penitentiary facilities across Serbia, with data collected from a sample of 590 inmates (86% male, ~ 40 years). Researchers were present during data collection, which primarily took place in groups of 30-40 individuals to ensure consistent oversight. The sample was diverse in terms of educational background but skewed toward lower educational attainment compared to the general population.
The study employed the Dirty Dozen inventory, which measures psychopathy, narcissism, and Machiavellianism through a 12-item scale, while sadism was evaluated using five items from the VAST inventory’s Direct Sadism scale. Participants also self-reported their number of biological children as a proxy for fertility. A “criminal career index” was developed by aggregating data from institutional records and participant histories. This index incorporated factors such as the age of first offense, the breadth of criminal activities, and assessments of risk and reoffending likelihood.
Initial analyses showed that psychopathy, Machiavellianism, sadism, and the criminal career index were negatively correlated with the number of children, while narcissism displayed no significant relationship. However, further regression analysis revealed that narcissism positively predicted fertility, with individuals high in narcissism reporting more offspring. Conversely, Machiavellianism and the criminal career index remained negative predictors, indicating that a history of persistent criminal behavior significantly reduced reproductive outcomes.
For psychopathy, the entire negative association with fertility was mediated by criminal behavior, suggesting that psychopathic individuals engaged in criminal activity experienced reduced reproductive fitness. Similarly, criminal behavior partially mediated the negative impact of Machiavellianism on fertility.
Interestingly, gender differences emerged, with criminal careers negatively affecting fertility in men but showing no significant impact on women.
Of note is that the cross-sectional design precludes causal inferences. Further, the sample limited to Serbian prisoners, may not generalize to broader populations.
Overall, this study highlights that while narcissism may confer reproductive advantages, other dark traits, particularly psychopathy and Machiavellianism, appear maladaptive when linked with persistent criminal behavior.
The study, “Reproductive ecology of dark personalities: Dark Tetrad traits, criminal career, and fertility,” was authored by Janko Međedović.