Hypothesis
Children with developmental language disorder would show weaker hand preference and less left-lateralised language, as earlier studies reported.
What failed
In 107 twin children with DLD and 156 typically developing twins aged 6–11, there were no group differences in handedness, functional transcranial Doppler language laterality, or consistency of left-hemisphere dominance. Right-lateralised language was in fact more common in the typically developing group (19.9% vs 9.3%), and links between laterality and language scores also did not replicate.
Broken assumption
Failure to establish typical left-hemisphere lateralisation is part of what goes wrong in developmental language disorder.
Why
Given the large sample and range of measures, the authors suggest earlier reports of atypical lateralisation in DLD may have been false positives.
From the published paper: Wilson et al. PeerJ, 2018. ↗CC BY