Types of language use and interference control in aging bilinguals: Insights from the Word–Color Stroop Task

Abstract This study investigates the relationship between bilingualism, language use, aging, and interference control using the Color–Word Stroop test task. We examined 158 highly proficient Basque–Spanish bilinguals and 84 Spanish monolinguals (aged 30–80 years) to test whether interference control declines with age and whether bilingual adaptations depend on language use frequency. Language experience was assessed using an adapted Language and Social Background Questionnaire and Color–Word Stroop test interference scores were analyzed by regression models. Results showed that interference control declines with age. Group-level differences between bilinguals and monolinguals were not significant once education was included as a covariate, although a small marginal advantage for bilinguals emerged when using education-adjusted T-scores. Within the bilingual group, higher use of the minority language (Basque) in social contexts was associated with significantly better interference control. Social language use showed a stronger relationship with interference control than home use. These findings highlight that bilingual advantages are not uniform but depend on language use frequency and context, contributing to understanding how bilingual experience shapes cognitive control across the lifespan.