Recent structural analyses of the widely used FIRO-B interpersonal personality measure identify a two dimensional model (Control and Social-Affect) rather than Schutz’s three dimensions of Control, Openness and Inclusion. The present study re-examined the FIRO model across the 54 individual items as reported by 89 adults. The results support a modified FIRO model of interpersonal personality in which Inclusion and Openness are part of the same substantive domain (Social Engagement), distinct from Control, but reflect different Generative and Accepted Modes of interaction. Importantly, however the analysis (SSA-I) reveals a subset of Schutz’s original Openness items that capture a third substantive component of the interpersonal domain, Social Withdrawal. This negative interpersonal tendency has not been identified previously within the FIRO or other interpersonal personality models.