Developmental changes in infants’ amodal phonological abstraction skills and their relationship to early vocabulary

Recent findings challenge the view that phonological abstraction emerges only after perceptual attunement. Four-month-olds can abstract an amodal place of articulation distinction between two artificial languages, well before attunement to native vowels (~7 months) and consonants (~10 months). Here, we followed the original 4-month-old cohort longitudinally, assessing their performance at 7 and 10 months (Experiment 1). Twenty-five Australian English-learning infants were trained to associate cartoon animals with audio-only words from contrasting mini-languages using only labial (e.g. bi-va-wo) versus only coronal consonants (e.g. dæ-zu-la). In the test phase, video-only novel words (talking face) were paired with congruent or incongruent animals. Infants looked longer at congruent trials at 4 months, indicating amodal abstraction, but showed no preference at 7 or 10 months. Abstraction scores did not predict receptive or expressive vocabulary at 13 or 25 months. Experiment 2 tested a separate cohort of 10-month-olds to examine potential confounding effects of the longitudinal design in Experiment 1. These infants showed a trend toward incongruency preference, opposite to the 4-month-olds. The effect reached significance when 10-month-olds from Experiment 1 were included in a post hoc analysis. Findings suggest phonological abstraction emerges early but evolves over the first year. Its lack of direct association with later vocabulary suggests abstraction may contribute to language development via intermediate processes.