Exploring the Dimensionality of the Social Skills Improvement System Using Exploratory Graph Analysis and Bifactor-(S - 1) Modeling.

Since its development over a decade ago, the Social Skills Improvement System (SSIS) has been one of the most widely used measures of social skills in children. However, evidence of its structural validity has been scant. The current study examined the original seven-factor and more recent five-factor structure (SSIS-SEL) of the self-report SSIS in a sample of English elementary school students (N = 3,331) aged 8 to 10 years (M = 8.66, SD = 0.59). A problematic fit was found for both structures with poor discriminant validity. Using exploratory graph analysis and bifactor-(S - 1) modeling, we found support for a four-factor structure, the variation of which was captured by a general factor defined by "empathy and prosocial skills." Future researchers, particularly those interested in using specific domains of the SSIS, are urged to assess its structure in their studies, if their findings are to be theoretically meaningful.