First-language acquisition in adolescence: evidence for a critical period for verbal language development.
Level 4 - case-series / case-control
Single-patient longitudinal case report
PubMed 9654433 · doi:10.1006/brln.1997.1943
What was done
Researchers tracked the language development of a young man (E.M.) who was profoundly deaf from birth, received no formal education, and had no contact with the deaf community. At age 15, he was fitted with hearing aids that corrected his hearing loss to 35 dB and began learning verbal Spanish. His verbal language development was observed over a 4-year follow-up period.
What was found
The abstract reports no numerical test scores or quantitative measures. The authors observed that over the 4-year period following hearing correction, E.M. demonstrated severe deficits in verbal comprehension and verbal production.
Why it matters
Because severe childhood linguistic deprivation is rare, this case provides observational evidence supporting the hypothesis that a critical period exists for acquiring a first verbal language.
Limits
The study is limited to a single participant (n = 1), precluding broad generalization. The abstract provides no standardized cognitive or linguistic metrics, and the effects of linguistic deprivation cannot be easily separated from broader developmental, educational, and social isolation.
Cited by
- contradicts The critical period for robust passive developmental neuroplasticity (such as learning multiple languages without an accent) typically closes around age 25.