Multi-method cross-linguistic validation of the Activism and Radicalism Intention Scale for adolescents

The world is rapidly changing, and many societies face radicalization involving activism and sometimes violence. Adolescents are at increased risk of radicalization, yet validated scales to assess violent and non-violent radical intentions among youth are lacking. This study aimed to validate the Activism-Radicalism Intention Scale (ARIS) for use among French- and English-speaking adolescents (14–18 years) using data from 1,911 Canadian high school students ( M age = 15.67; SD age = 0.98). We employed confirmatory factor analysis (CFA) and Rasch analysis to evaluate the scale’s dimensionality, reliability, validity, and invariance across sociodemographic factors. The CFA supported distinct Activism Intention Scale (AIS) and Radicalism Intention Scale (RIS) for both language versions of the scale. The Rasch analysis provided item-level diagnostics for each subscale, with satisfactory model fit indices observed for both the AIS and RIS. Both the CFA and Rasch supported the scales’ reliability and convergent and structural validity, including its measurement invariance across languages, age, and gender. An algorithm for converting ordinal data into interval-level scores using Rasch estimations was developed to enhance the precision of the scales. Both the validated ordinal and interval-level scores of the ARIS provide evidence of its robustness for assessing violent and non-violent radical intentions in adolescents across the two languages.