Abstract
The causal role of speed of processing (SOP) in developmental language disorder (DLD) is unclear given that SOP has been implicated in other neurodevelopmental disorders such as Attention-Deficit/Hyperactivity Disorder (ADHD). This study investigated associations between SOP, language, and inattention/hyperactivity in a UK epidemiological cohort (N=528). Monolingual children from a range of socio-economic backgrounds were assessed longitudinally; at ages 5-6 (2012/13) and 7-8 years (2014/15). Persistent weaknesses in SOP characterised children with DLD but did not predict language longitudinally. Ratings of inattention/hyperactivity moderated the association between SOP and language, indicating that SOP deficits are particularly detrimental for language when coupled with poor attention/hyperactivity. SOP may be a shared risk factor for DLD and inattention/hyperactivity or a general marker of neurodevelopmental disorder.