The role of grandiose and vulnerable narcissism in self-reported and laboratory aggression and testosterone reactivity

• Grandiose narcissism predicted behavioral, reactive, and proactive aggression and testosterone response.
• Vulnerable narcissism predicted self-reported aggression but was irrelevant to behavior and testosterone.
• Testosterone responses in aggression depend on both situational context and trait.
• Grandiose narcissism may contribute more than vulnerable narcissism to externalizing aggression.

This experiment aimed to identify narcissistic risk factors for aggression. Grandiose narcissism, the more familiar form of narcissism involving overt assertion of personal superiority, was differentiated from vulnerable narcissism, which is found in people who present themselves as shy and humble. Aggression was measured in multiple ways, including laboratory behavior, self-report measures (reaction to provocation and proactive, instrumental aggression were measured separately), and hormonal reactivity (testosterone). Grandiose narcissism predicted behavioral, reactive, and proactive aggression and testosterone response. Vulnerable narcissism predicted self-reported aggression but was irrelevant to behavior and testosterone. Thus, testosterone responses in aggression depend on both situational context and trait, and grandiose narcissism may contribute more than vulnerable narcissism to externalizing aggression.