Development and Validation of the Ultra-Short Version of the Identity Style Inventory (US-ISI-5) Among Czech Adolescents

Adolescence and the transition to adulthood represent critical periods for identity formation, with a coherent and stable sense of identity being a key component of psychosocial development and functioning in different social roles throughout one’s life. In their decision-making processes, individuals mainly employ three socio-cognitive strategies – informational, normative, and diffuse/avoidant – each of which can be measured by the Identity Style Inventory (ISI). However, the traditional version of this scale is too long and not particularly suitable for online surveys. This research note aims to develop and validate an ultra-short version of the ISI with a large sample of Czech adolescents aged 15–20 (N = 21,968). The analysis is based on data collected online from the first wave of the Czech Education Panel Survey (CZEPS), administered in autumn 2023. Exploratory (EFA) and confirmatory factor analyses (CFA) were conducted during the development process. The validation and psychometric properties were evaluated in terms of reliability, convergent and criterion-related validity, and measurement invariance across gender and type of study. The results showed that the ultra-short Czech version of the ISI scale with nine items achieved good psychometric and structural quality. EFA clearly supported the three-factor structure, which was confirmed by CFA with good model fit. The reliability assessment results were consistent with those of other studies, and in terms of validity, both convergent and criterion-related validity were demonstrated by weak but theoretically consistent and meaningful associations with other measures. In terms of measurement invariance, partial scalar invariance was achieved across gender and type of study. The newly developed ultra-short nine-item version of the ISI (US-ISI-5) has been validated as a psychometrically sound and useful instrument for measuring identity processing strategies among Czech adolescents.