This paper reports a study that used a quasi-experimental design to examine if a career intervention designed to increase self-knowledge enabled self-discovery or self-construction, determined by the structure of the personality inventory used. This study, situated within the theoretical model of Markus's research in self-schemata (1977), used instruments that measured the Big Five personality factors. Results showed that after only one exercise designed to increase self-knowledge, high school students in the experimental group elaborated "self-schemata" that encompassed the five dimensions corresponding to the structure of the instrument used. Findings suggested that the self-knowledge tool constituted a sort of structured "looking glass" in which young people saw themselves reflected according to the dimensions in the inventory used.