Delayed Early Vocabulary Development in Children at Family Risk of Dyslexia

Area of Science:

• Developmental Psychology
• Linguistics
• Neuroscience

Background:

• Early vocabulary development is crucial for reading acquisition.
• Children with a family risk (FR) of dyslexia may exhibit early language delays.
• Understanding these early trajectories can inform interventions.

Purpose of the Study:

• To investigate the longitudinal relationship between early vocabulary growth and dyslexia risk.
• To examine vocabulary trajectories in children with and without a family risk of dyslexia.
• To determine if vocabulary development differs in children who later develop dyslexia.

Main Methods:

• Longitudinal study of 212 children from the Dutch Dyslexia Program.
• Parental reports on receptive and expressive vocabulary size at 17, 23, 29, and 35 months.
• Analysis of dyslexia status at age 8, categorizing children into FR-dyslexic, FR-nondyslexic, and typically developing (TD) groups.

Main Results:

• FR-dyslexic children had lower receptive vocabulary from 23 months and expressive vocabulary from 17 months compared to FR-nondyslexic children.
• Latent growth curve modeling revealed lower initial vocabulary growth rates in FR-dyslexic children, followed by partial recovery.
• No significant differences were found between FR-nondyslexic and TD children's vocabulary development.

Conclusions:

• Early receptive and expressive vocabulary deficits are associated with later reading outcomes.
• Vocabulary growth in FR-dyslexic children is characterized by a delay rather than a deviation from typical development.
• Vocabulary size and growth patterns can serve as an additional risk factor for identifying dyslexia.