FACTORS AFFECTING VOCABULARY DEVELOPMENT IN DEAF AND HARD-OF-HEARING CHILDREN AGED 2-3 WITH COCHLEAR IMPLANTS: A RESEARCH REVIEW

This systematic review synthesizes over 30 studies published in international scientific journals, identifying six key factor groups influencing vocabulary development in 2 to 3-year-old deaf and hard of-hearing children with cochlear implants – a period recognized as the critical window for spoken language acquisition. The findings suggest that vocabulary development in this population is multifactorial, with the communication environment, caregivers’ and educators’ competence, and the quality of intervention playing decisive roles. The paper proposes an integrated, multi-layered framework (developmental, audiological, educational, and social) to guide future research and early-intervention programs in Vietnam aimed at optimizing spoken language outcomes for young children with cochlear implants.