Introducing the Narcissistic Antagonism Scale: A missing puzzle piece in the assessment of momentary narcissism.

Narcissism is a relatively stable personality trait, which is most accurately described by three facets: agentic, antagonistic, and neurotic. Existing studies support the central role of antagonistic narcissism and its role in explaining the process of fluctuation in narcissism. However, there is a lack of a suitable adjective-based measure of antagonistic narcissism, resulting in intensive longitudinal studies assessing only agentic and neurotic narcissism. To address this gap and to advance research on fluctuations in narcissism, this article introduces the Narcissistic Antagonism Scale (NAS). Across six studies (total N = 1,862; k = 14,927 observations), we establish the NAS's factorial, convergent, and divergent validity; reliability; and temporal stability. The three-factor model of narcissism, including antagonistic aspects, reproduces and proves to be invariant across daily and momentary perspectives. The NAS exhibits good psychometric properties at both between- and within-person levels. It is a valuable addition for intensive longitudinal studies and facilitates a nuanced examination of narcissistic states across diverse contexts. (PsycInfo Database Record (c) 2024 APA, all rights reserved).