Purpose: In this study, the authors examined (a) whether children with specific language impairment (SLI) can implicitly compute the probabilities of adjacent sound sequences, (b) if this ability is related to degree of exposure, (c) if it is domain specific or domain general and, (d) if it is related to vocabulary.
Method: Children with SLI and normal language controls (ages 6;5-14;4 [years;months]) listened to 21 min of a language in which transitional probabilities within words were higher than those between words. In a second study, children with SLI and Age-Nonverbal IQ matched controls (8;0-10;11) listened to the same language for 42 min and to a second 42 min "tone" language containing the identical statistical structure as the "speech" language.
Results: After 21 min, the SLI group's performance was at chance, whereas performance for the control group was significantly greater than chance and significantly correlated with receptive and expressive vocabulary knowledge. In the 42-minute speech condition, the SLI group's performance was significantly greater than chance and correlated with receptive vocabulary but was no different from chance in the analogous 42-minute tone condition. Performance for the control group was again significantly greater than chance in 42-minute speech and tone conditions.
Conclusions: These findings suggest that poor implicit learning may underlie aspects of the language impairments in SLI.