Speech-sound discrimination in school-age children: psychophysical and neurophysiologic measures

This study measured behavioral speech-sound discrimination and a neurophysiologic correlate of discrimination in normal school-age children (ages 6 to 15) to determine if developmental effects exist. Just noticeable differences (JNDs) and mismatch responses (MMNs) were assessed for synthetic syllables that differed in third-formant onset frequency (/da-ga/) and formant transition duration (/ba-wa/). These stimuli were selected because children with learning problems often find it difficult to discriminate rapid spectrotemporal changes like /da-ga/, whereas the ability to distinguish /ba-wa/ is relatively unimpaired. Results indicate that JNDs for /da-ga/ show no developmental effects and that JNDs for /ba-wa/ decrease slightly with age (although likely for task-related reasons). MMNs elicited by two /da-ga/ stimulus pairs (onset frequency differences = 20 Hz, 280 Hz) and three /ba-wa/ stimulus pairs (transition duration differences = 3, 5, 15 ms) showed no systematic or significant differences for onset latency, duration, or area as a function of age. Normative JND and MMN data are provided. These norms provide a metric against which children with suspected central auditory processing difficulties or auditory-based language disorders can be compared.