Theory of mind and explicit mentalizing: vocabulary as a mediator in preschoolers with and without a history of language delay

This study examined explicit mentalising (EM) in preschoolers with a history of language delay (HLD) and tested whether vocabulary mediates the association between theory of mind (ToM) and EM, after controlling for family socio-economic status (SES). Ninety Mandarin-speaking preschoolers (45 with HLD, 32 boys; 45 without HLD, 24 boys; aged 4-6 years) completed measures of cognitive and affective ToM, receptive emotional and non-emotional vocabulary, expressive emotional and non-emotional vocabulary, and EM. The results showed that participants with HLD scored lower on vocabulary, ToM, and EM than their peers without HLD. Expressive vocabulary partially mediated the ToM-EM relationship. For cognitive ToM, mediation followed a sequential path from receptive to expressive vocabulary, whereas affective ToM was mediated only by expressive vocabulary; the association of nonemotional expressive vocabulary in the cognitive pathway was attenuated after controlling for SES. EM interventions for preschoolers with HLD may benefit from targeting reasoning processes and supporting the development of emotional understanding and expression through vocabulary growth and ToM-related mechanisms.