The Self-Extension Dimensional Assessment: An Instrument Development Study

The self is thought to be malleable, capable of being extended beyond the physical body and into a variety of things, such as friends, family, and even possessions. However, methods of measuring self-extension as a multidimensional construct are scarce. Using three separate samples (total N of all samples = 646), the authors developed and examined a new measure (the self-extension dimensional assessment [SEDA]) capable of assessing five primary self-extension dimensions (SEDs): (a) intrapersonal, (b) interpersonal, (c) collective, (d) spatial-material, and (e) transpersonal. To this end, principal component analysis (PCA) and bifactor exploratory structural equation modeling (ESEM) were used to determine whether data supported the proposed, five-part self-extension system. A secondary aim of the present study was to assess the convergent validity of the SEDA, using bivariate correlations to explore the five SEDs in relation to extant instruments measuring related forms of self-representation, the Big Five personality factors, and two markers of psychological health (psychological well-being and emotional distress). Results indicated that the 14-item SEDA is a psychometrically sound instrument that captures five theoretically grounded dimensions of self-extension. The SEDA may be a valuable measurement tool for more comprehensively assessing individual differences in the experience of self-extension.