The state-trait sense of self inventory: A psychometric study of self-experience and its relation to psychosis-like manifestations

The sense of self is a fundamental construct in the study of the mind, yet its psychological nature remains elusive. We introduce a novel 25-item inventory to investigate selfhood both as an enduring trait and a temporary state. We hypothesized two foundational aspects of the self: identity (related to self-referencing and continuity over time) and agency (the perception of controlling own's actions and thoughts). Results from two population studies highlight a singular self-trait factor combining agency and identity. In contrast, self-state measures revealed a bifactorial structure with a high-order factor and three lower-order subfactors: state-identity, state-agency, and state-technology. These factors were predictive of psychosis-like experiences, schizotypal traits, and hopelessness. Mediation analysis demonstrated that the negative association between the sense of self and hopelessness is mediated by depressive manifestations. Our research provides a tool to shed new light on the complexity of the sense of self and its mental health implications.