Backward and Simultaneous Masking in Children With Grammatical Specific Language Impairment: No Simple Link Between Auditory and Language Abilities Purpose: We investigated claims that specific language impairment (SLI) typically arises from nonspeech auditory deficits by measuring tone-in-noise thresholds in a relatively homogeneous SLI subgroup exhibiting a primary deficit restricted to grammar (Grammatical[G]-SLI). Method: Fourteen children (mostly teenagers) with G-SLI were compared to age-, vocabulary-, and grammar-matched control children on their abilities to detect a brief tone in quiet and in the presence of a masking noise. The tone occurred either simultaneously with the noise or just preceding it (backward masking). Maskers with and without a spectral notch allowed estimates of frequency selectivity. Results: Group thresholds for the G-SLI children were never worse than those obtained for younger controls but were higher in both backward and simultaneous masking than in age-matched controls. However, more than half of the G-SLI group (8/14) were within age-appropriate limits for all thresholds. Frequency selectivity in the G-SLI group was normal. Within control and G-SLI groups, no threshold correlated with measures of vocabulary, grammar, or phonology. Nor did the language deficit in the G-SLI children vary with the presence or absence of auditory deficits. Conclusion: The auditory processing deficits sometimes found in children with SLI appear unlikely to cause or maintain the language impairment. KEY WORDS: specific language impairment, auditory processing disorder, masking, backward masking, simultaneous masking S pecific language impairment (SLI) is a developmental disorder af- fecting about 7% of the population, in which language acquisition is impaired in an otherwise apparently typically developing (TD) child (Bishop, 1997; Leonard, 1998). Two general types of explanations have been popular in attempting to account for SLI. The first posits that SLI arises from linguistic deficits (the domain-specific view), in particular in systems and processes relating to grammar: syntax, morphology, and pos- sibly phonology, too (Rice, 2003; van der Lely, 2005; van der Lely & Battell, 2003; van der Lely, Rosen, & McClelland, 1998). In contrast to this is a domain-general explanation, inspired by earlier work of Efron (1963), that impaired auditory processing is the core deficit of SLI (Tallal & Piercy, 1973a, 1973b, 1974, 1975). This view posits that an auditory deficit (espe- cially affecting the perception of rapidly changing or transient sounds) causes impoverished input to the developing language system, leading to impaired speech perception, poor phonological representations and Stuart Rosen Alan Adlard Heather K. J. van der Lely University College London Journal of Speech, Language, and Hearing Research • Vol. 52 • 396–411 • April 2009 • D American Speech-Language-Hearing Association 1092-4388/09/5202-0396 396