Brief report: cross-cultural evidence for the heterogeneity of the restricted, repetitive behaviours and interests domain of autism: a Greek study.

The team looked at 153 Greek children already diagnosed with autism. They used the same checklist American teams use to score restricted and repetitive behaviors (RRBI).

Next they ran a principal-component analysis. This is a math tool that groups checklist items that move together. It shows if the domain is one blob or has smaller parts.

Two clear chunks popped out, just like in U.S. data. One chunk is 'Insistence on Sameness' (rigid routines, same food, same route). The other is 'Repetitive Sensory & Motor Behaviors' (hand flaps, spinning, sensory seeking).

Because the same split showed up in Greece, the two-factor picture is not just an American quirk. It looks like a stable cross-cultural pattern.

Bhat et al. (2023) did a similar cross-check on the DCD-Q motor form. They also found the original factor map needed finer slices. Together these studies tell us: single-domain scores can hide real sub-groups in autism.

Kaplan-Kahn et al. (2026) tested the Parenting Stress Index and, like Vaya, rejected the old three-factor model. Their six-factor version gave clearer stress profiles. The message across papers is the same—factor analysis keeps showing that our old 'one score fits all' tools are too blunt.

Older European validations (English et al. (1995), Oliver et al. (2002)) proved you can translate checklists into Dutch or Swedish and still get decent totals. Vaya pushes that idea further by showing the inner structure, not just the total, travels across languages.

When you write goals, split RRBI into sameness items and sensory-motor items. Track them on separate graphs. A child might drop hand flaps yet still need daily picture schedules, or vice versa. Using one merged score would miss that change and waste teaching time.