Input and Processing Factors Affecting Infants' Vocabulary Size at 19 and 25 Months

Area of Science:

• Developmental Psychology
• Linguistics
• Child Language Acquisition

Background:

• Individual differences in early vocabulary development are influenced by various factors.
• Understanding the interplay between maternal speech and infant perception is crucial for early language acquisition.

Purpose of the Study:

• To investigate the relative contributions of maternal speech quantity, maternal speech acoustic quality, and infant word recognition to vocabulary development.
• To determine how these factors predict vocabulary size at different developmental stages (19 and 25 months).

Main Methods:

• Collected speech recordings from 48 mothers at infant age of 17 months to assess speech quantity and quality.
• Assessed infant word recognition abilities through a perception experiment at 19 months.
• Correlated these measures with infant vocabulary size at 19 and 25 months.

Main Results:

• Maternal speech quantity was the strongest predictor of vocabulary size at 19 months.
• Infant word recognition at 19 months became a better predictor of vocabulary size at 25 months.
• Maternal speech acoustic quality did not correlate with vocabulary size at either age.

Conclusions:

• Early vocabulary growth is significantly influenced by the quantity of maternal speech and infant word recognition abilities.
• The predictive power of infant word recognition increases as children develop, suggesting a shift in learning mechanisms.
• Findings underscore the importance of multifaceted approaches to understanding and supporting early word learning.