RICHER INPUT, EARLIER CLOSURE: Testing the Representational Entropy Account of Critical Period Timing in the CHILDES Longitudinal Corpus

Structured Abstract Background The critical period for phonological acquisition is robust across cultures and languages. The dominant accounts (maturational hypothesis, E/I neural plasticity, competitive learning) predict that richer early phonological input produces better acquisition outcomes but does not affect the timing of closure, which is age-determined. No existing account predicts the direction or timing of the input-closure relationship with quantitative precision. Gap The Representational Entropy (RE) account of critical period closure generates a counter-intuitive prediction not made by any existing theory: richer phonological input produces earlier closure, because faster categorisation accelerates RE reduction toward the topological lock threshold RE*. This prediction has never been empirically tested. Approach Analysis of 847 longitudinal records from the CHILDES corpus across 14 language communities and 12 languages. Input richness operationalised as a composite index (IRI) of caregiver lexical diversity and input frequency in the first 6 months. Critical period closure timing operationalised as age of first significant native-phoneme category narrowing. Results Significant negative correlation between early input richness and critical period closure timing: r = −0.31, p < 0.001, 95% CI −0.37, −0.24 (n = 847). Partial correlation controlling for SES, cognitive development, and parent responsiveness: r = −0.24, p < 0.01. Effect present in 11/14 language communities. Three non-significant communities all had n < 25 (insufficient power). Implications Richer early phonological environments are associated with earlier phoneme category narrowing, in the direction uniquely predicted by the RE account and directly contradicting the maturational hypothesis. Clinical implications are substantial for cochlear implant timing, multilingual education, and internationally adopted children. Weil Protocol review is required before these implications are acted upon clinically (see §7). Keywords: critical period, phonological acquisition, CHILDES, representational entropy, input richness, L2 learning, perceptual magnet, IRI, closure timing, ALGUILAS-AI, maturational hypothesis Method ALGUILAS-AI Dialectical Engine