Modeling the relationships among sustained attention, short-term memory, and language in Down syndrome
Introduction: Language is poorer than expected given developmental level in youth with Down syndrome (DS). This study sought to determine if predictors of language difficulty in DS include sustained attention (SA) and short-term memory (STM). Specifically, I hypothesized indirect effects of SA (auditory and visual) on language (receptive and productive vocabulary and syntax) through STM (auditory and visual) controlling for age and nonverbal ability. Method: Thirty-five youth with DS aged 10- to 22-years-old participated in this study. To measure SA, participants completed auditory and visual SARTs in which they pressed a computer key in response to non-targets and resisted pressing a key in response to the target. Outcomes were omissions (failing to respond to non-targets) and commissions (responding to the target). Span tasks were used as measures of STM, and standardized tasks were used as measures of language and nonverbal ability. For main statistical analyses, simple mediation models were run with the bootstrapping method. Results: Potential indirect effects of auditory SA on language through auditory STM were supported by correlations, though the same was not true for the visual domain. For auditory SA, separate models were run for omissions and commissions. All nine models considering indirect effects of auditory omissions on language through auditory STM controlling for age and nonverbal ability were significant, with point estimates ranging from -.24 to -.31 and no 95% confidence intervals crossing zero. Specifically, outcomes were general language, receptive language, productive language, vocabulary, syntax, receptive vocabulary, receptive syntax, productive vocabulary, and productive syntax. None of nine models considering auditory commissions were significant. Discussion: SA predicts language through STM in youth with DS. Specifically, lapses in auditory SA (as indicated by increased omissions) predict poorer receptive and productive vocabulary and syntax through auditory STM. The same was not true for the inhibitory component of SA (commissions) or for the visual modality more generally. Results have immediate implications for language therapy with youth with DS. That is, addressing auditory SA in therapy could lead to improved language outcomes in DS. Thus, interventions geared toward improving auditory SA in DS should be piloted.