Perceptual Learning and Predictability of Children's Speech

Purpose: According to theoretical models, perceptual learning is modulated by the level of acoustic predictably in the speech signal. This study investigated whether the variable speech of children is learnable in a perceptual learning paradigm and examined whether speech variability, as quantified by the acoustic spatiotemporal index (STI), predicted perceptual learning outcomes. Method: Speech samples were elicited from 40 typically developing children talkers (ages 3–8 years) and presented to 410 adult listeners in a structured perceptual learning experiment. Listeners transcribed phrases before (pretest) and after (posttest) a lexically guided familiarization phase. Intelligibility improvements following familiarization were analyzed using paired t tests, and regression analyses examined whether acoustic STI values predicted perceptual learning outcomes. Results: Listeners demonstrated significant perceptual learning of children's speech, with an average intelligibility gain of 6.4% following familiarization ( p < .001). Regression analyses revealed a significant interaction between STI and pretest intelligibility: Lower STI values (indicating more predictable speech) were associated with greater intelligibility gains but only when pretest intelligibility was sufficiently low. Conclusions: This study provides the first empirical evidence that children's speech is learnable in a structured perceptual learning paradigm. Although the acoustic STI affords some insight into predictability, it does not fully account for variability in perceptual learning. Future work should explore measures that capture segmental predictability to refine models of speech learnability.