Abstract
The relationship between narcissism and aggression has received considerable research attention, with the main conclusion being that individuals with higher levels of narcissism tend to exhibit more aggressive behavior. However, most evidence comes from cross-sectional and experimental studies using between-person analyses and relies heavily on Western convenience samples, leaving the temporal dynamics and within-person processes largely unexplored. This preregistered study examined four large-scale data sets of Chinese undergraduates and offenders: two ambulatory assessment samples (427 undergraduates and 775 offenders; 19,331 and 42,820 observations, respectively) and two long-term longitudinal samples (N = 1,404, 969, 822, 613 for undergraduates and 2,064, 1,716, 1,609, 1,393 for offenders, each with four assessments over a year). Results indicated that narcissism and aggression prospectively predicted one another at the momentary level, but not the long-term level. These reciprocal effects were largely replicated across undergraduate and offender samples. Person-level narcissism and aggression moderated several of these dynamic associations, with the most robust pattern showing that higher person-level aggression consistently strengthened the effects of narcissistic states on subsequent aggression among offenders. Overall, this study provides, to our knowledge, the first within-person evidence for dynamic reciprocal associations between narcissism and aggression, while also offering stronger support for the robustness, cultural generalizability, and population representativeness of these processes. (PsycInfo Database Record (c) 2026 APA, all rights reserved).