Self-Other Differentiation Scale: Dimensionality, IRT Parameterization, and Measurement Invariance

The Self-Other Differentiation Scale (Olver, Aries, & Batgos, 1989) is a self-report instrument assessing the experience of a separate sense of self from others. The authors aimed to examine its dimensionality, reliability, and measurement invariance across gender. It was completed by 348 participants (48% men) from 17 to 30 years old in Study 1, 348 participants (40% men) from 18 to 28 years old in Study 2, and 1,068 participants (49% men) from 17 to 28 years old in Study 3. The results supported the hypothesis of just one factor underlying the scale; they also showed an appropriate internal consistency and a partial measurement invariance across gender. Results also showed evidence for a 10-item version of the scale. Globally, the Self-Other Differentiation Scale can be considered a good scale to assess individual's sense of differentiation of one's own sense of self from others.