We present a core-concept model (CCM) suggesting that stimulus centrality is an important factor in category representations in implicit measures. We tested the hypothesis that idiographic stimuli (first name, birthday) are more central and therefore assess self-concept in Implicit Association Tests (IATs) more validly than generic and nonspecific stimuli (me, you). Superior validity of the idiographic variant emerged across three different domains of self-concept. First, an idiographic self-esteem IAT displayed higher correlations than a generic IAT with self-assessments and observer-assessments of self-esteem. Second, an idiographic body scheme-IAT predicted subjective ratings of body image and objective body-mass index. Third, an idiographic aggressiveness-IAT had higher incremental validity for unprovoked aggression when interacting with explicit measures of aggressiveness. We conclude that idiographic stimuli focus participants' attention on the core features of the self, hence, tapping into self-related associations to a stronger degree than generic stimuli. Copyright © 2011 John Wiley & Sons, Ltd.