1. Introduction
The Internet has become indispensable in modern society, with rapidly evolving technologies and diverse social media functions. However, this environment also creates greater opportunities for online misconduct, such as trolling, identity theft, and cyberbullying. Dark Tetrad traits (Machiavellianism, psychopathy, narcissism, and sadism) are key predictors of deviant behavior, yet their influence on cyber deviance through online disinhibition remains unclear. Although Cyber-Routine Activity Theory has emphasized victims, a fuller understanding requires attention to perpetrators' psychological mechanisms, particularly the mediating role of online disinhibition.


2. Purpose
This study aimed to examine a mediation model in which online disinhibition explains the relationships between the Dark Tetrad traits and adults' cyber deviance, thereby providing a more comprehensive understanding of online deviant behavior in the digital age.


3. Method
A total of 454 Taiwanese adults (58% female; M = 26.98, SD = 8.27), all of whom reported daily Internet use, completed questionnaires measuring Dark Tetrad, online disinhibition, and cyber deviance. Path analysis with 5,000 bootstrapped samples was used to test mediation effects.


4. Results
Direct effects of the Dark Tetrad traits on cyber deviance were not significant. However, online disinhibition mediated the effects of psychopathy (β = .04, 95% CI [.01, .07], p = .03), narcissism (β = -.04, 95% CI [-.07, -.01], p = .01), and sadism (β = .03, 95% CI [.01, .04], p = .01) on cyber deviance. No mediating effect was found for Machiavellianism. The model accounted for 10% of the variance in online disinhibition and 6% in cyber deviance.


5. Conclusion
Findings indicate that psychopathy and sadism increase online disinhibition, thereby fostering more cyber deviance, while narcissism reduces disinhibition and decreases deviance. These results highlight the need for policies and educational interventions to address misperceptions that cyberspace is free from accountability. Strengthening awareness of digital traceability technologies may help reduce deviant online behaviors.