Repetitive Behaviours in Williams Syndrome: A Cross‐Cultural Comparison Between the United Kingdom and Japan

BACKGROUND: Williams syndrome (WS) is a relatively rare neurodevelopmental condition characterised by distinctive cognitive and behavioural phenotypes, including restricted and repetitive behaviours (RRBs). Although cross-cultural studies suggest that caregiver reports of autism-related RRBs may be culturally subjective, little is known about whether caregiver-reported RRB profiles in WS are similar across cultural contexts. Additionally, because RRB profiles may vary with age, examining cross-sectional age-related patterns is important. This study explored between-country variation and cross-sectional age-related patterns in caregiver-reported Repetitive Behaviour Questionnaire (RBQ) scores among individuals with WS in the United Kingdom and Japan. METHODS: Eighty primary caregivers of individuals with WS from Japan (n = 40) and the United Kingdom (n = 40) completed the Repetitive Behaviour Questionnaire (RBQ). Bayesian negative binomial regression models were used to examine between-country differences and cross-sectional age-related associations in caregiver-reported RBQ total, sensory/motor and sameness/circumscribed interests scores. RESULTS: UK caregivers reported directionally higher Total RBQ and Sameness/Circumscribed Interests scores than Japanese caregivers, with the clearest contrast observed for the Sameness/Circumscribed Interests domain. No clear evidence of a between-country difference was found for caregiver-reported Sensory/Motor Behaviours scores, although a weak directional tendency toward higher UK scores was observed. Moreover, age showed weak cross-sectional negative trends for total RBQ and Sensory/Motor Behaviours scores, although these estimates were imprecise and were attenuated in the verbal mental age-adjusted analyses. CONCLUSIONS: These findings are consistent with previous studies of caregiver-reported RRBs among autistic individuals, suggesting that insistence on sameness and circumscribed interests may be reported differently across cultural contexts. In WS, caregiver-reported RBQ profiles may vary by cultural context and show tentative cross-sectional age-related patterns, highlighting the need to consider contextual and developmental factors when interpreting parent-report measures of these behaviours.