Sensitive periods in language learning
A declining average learning rate does not imply that adults cannot learn.
The question
How do age, exposure and learning opportunity shape second-language attainment?
Critical-period research distinguishes the age at which learning begins from the amount learned and the eventual level reached. These are related but different quantities.
What the claims mean
Age-related capacity
Changes in learning mechanisms with maturation may constrain later attainment even with extensive practice.
Experience and selection
Exposure, education, language use and who enters a study also vary with age. They must be considered before attributing an age curve entirely to biology.
Evidence to examine
Hartshorne, Tenenbaum and Pinker (2018) analyzed a large English grammar dataset and modeled age-related changes in learning. Their design explicitly separates learning ability from ultimate attainment. The findings concern that grammar measure, not a single deadline for all language skills.
Shared ground and disagreement
What the accounts can share
Age of acquisition and experience matter. Vocabulary, pronunciation and grammatical performance need not share an identical developmental trajectory.
What remains at issue
The shape and mechanism of age-related change, and how well an estimate generalizes across languages, learning environments and measures.
Limits and next tests
Large online samples can still be selective. A model’s estimated boundary is not a prediction of what a particular adult can achieve or a reason to discourage later study.
What would help distinguish the claims?
Combine longitudinal studies with well-characterized exposure and multiple skill measures. Compare models of gradual change and sharper transitions on new language populations.
Textbook connection
ContextualOpenStax Psychology 2e: 7.2 Language
The section provides background vocabulary. It does not cover the full debate or establish the status of later research.
Sources and access
- Hartshorne, J. K., Tenenbaum, J. B., & Pinker, S. (2018). A critical period for second language acquisition: Evidence from 2/3 million english speakers. Cognition, 177, 263–277. https://doi.org/10.1016/j.cognition.2018.04.007Consulted sourceAbstract inspected
Primary bibliographic record and complete abstract retrieved from Europe PMC on October 21, 2026. Full paper methods and supplements were not inspected.