The role of vision in the acquisition of words: Vocabulary development in blind toddlers

What is vision's role in driving early word production? To answer this, we assessed parent-report vocabulary questionnaires administered to congenitally blind children (N = 40, Mean age = 24 months [R: 7–57 months]) and compared the size and contents of their productive vocabulary to those of a large normative sample of sighted children (N = 6574). We found that on average, blind children showed a roughly half-year vocabulary delay relative to sighted children, amid considerable variability. However, the content of blind and sighted children's vocabulary was statistically indistinguishable in word length, part of speech, semantic category, concreteness, interactiveness, and perceptual modality. At a finer-grained level, we also found that words’ perceptual properties intersect with children's perceptual abilities. Our findings suggest that while an absence of visual input may initially make vocabulary development more difficult, the content of the early productive vocabulary is largely resilient to differences in perceptual access.

Research Highlights

• Infants and toddlers born blind (with no other diagnoses) show a 7.5 month productive vocabulary delay on average, with wide variability.
• Across the studied age range (7–57 months), vocabulary delays widened with age.
• Blind and sighted children's early vocabularies contain similar distributions of word lengths, parts of speech, semantic categories, and perceptual modalities.
• Blind children (but not sighted children) were more likely to say visual words which could also be experienced through other senses.