Leaders’ Dark Tetrad and their effectiveness: An analysis of the curvilinear relationships mediated by team members’ knowledge-sharing behaviors

Abstract

This study examined how leaders’ Dark Tetrad traits - narcissism, Machiavellianism, psychopathy, and sadism - relate to perceived leadership effectiveness, and whether team members’ knowledge-sharing behaviors mediate these associations. Curvilinear regression analyses conducted with a sample of 217 employees revealed that narcissism exhibited an inverted U-shaped relationship with leadership effectiveness. In contrast, Machiavellianism, psychopathy, and sadism were only negatively and linearly associated with leader effectiveness. Regarding knowledge-sharing, sadism demonstrated a significant curvilinear (U-shaped) relationship, while other traits yielded either weak or non-significant patterns. Knowledge-sharing itself followed an inverted U-shape curvilinear path in predicting leadership effectiveness. Knowledge-sharing behaviors did not mediate the relationship between Dark Tetrad traits and leadership effectiveness. These findings suggest that dark traits may display context-dependent adaptability, particularly at moderate levels, challenging traditional linear models in leadership research. They highlight the role of nonlinear dynamics in effective leadership. Limits and future directions are presented.