Speech perception and phonological short-term memory capacity in language impairment: Preliminary evidence from adolescents with SLI and ASD Running Head: Speech perception and STM in language impairment

Background: The cognitive bases of language impairment in specific language impairment (SLI) and autism spectrum disorders (ASD) were investigated in a novel nonword comparison task which manipulated phonological short term memory (PSTM) and speech perception, both implicated in poor nonword repetition. Aims: This study aimed to investigate the contributions of PSTM and speech perception in nonword processing and whether individuals with SLI and ASD plus language impairment (ALI) show similar or different patterns of deficit in these cognitive processes. Method & Procedures: Three groups of adolescents (aged 14 to 17), 14 with SLI, 16 with ALI, and 17 age and nonverbal IQ matched typically developing (TD) controls, made speeded discriminations between nonword pairs. Stimuli varied in PSTM load (2or 4syllables) and speech perception load (mismatches on a word-initial or word-medial segment). Outcomes & Results: Reaction times showed effects of both nonword length and mismatch position and these factors interacted: 4-syllable and word-initial mismatch stimuli resulted in the slowest decisions. Individuals with language impairment showed the same pattern of performance as those with typical development in the reaction time data. A marginal interaction between group and item length was driven by the SLI and ALI groups being less accurate with long items than short ones, a difference not found in the TD group. Conclusions: Nonword discrimination suggests that there are similarities and differences between adolescents with SLI and ALI and their TD peers. Reaction times appear to be affected by increasing PSTM and speech perception loads in a similar way. However, there was some, albeit weaker, evidence that adolescents with SLI and ALI are less accurate than TD individuals, with both showing an effect of PSTM load. This may indicate, at some level, the processing substrate supporting both PSTM and speech perception may be intact in