Abstract
Children diagnosed with autism often present with an atypical discrepancy between their receptive and expressive language levels, or an atypical receptive-expressive language phenotype. Children with an atypical receptive-expressive phenotype present with a relative receptive language advantage (expressive level < receptive level) or a relative expressive language advantage (expressive level > receptive level), whereas those with a typical phenotype have balanced receptive and expressive language levels. It remains unclear whether atypical receptive-expressive language phenotypes are evident before 24 months in children with autism features or whether they are associated with concurrent child developmental functioning or later language growth. Participants (N = 80) were drawn from a randomized comparative efficacy intervention study for 12-23-month-olds with autism features and elevated scores on an autism diagnostic instrument. Baseline receptive and expressive language age equivalent (AE) scores were used to describe continuous variation in receptive-expressive language phenotypes by quantifying the gap between each child's receptive and expressive language levels. These continuous metrics were then used to classify children into discrete language profile groups: expressive advantage (EA), receptive advantage (RA), and balanced. On average, children had a gap of three AE "months" between their receptive and expressive language levels. Over 75% of children presented with an atypical receptive-expressive phenotype (40% EA profile, 36% RA profile), whereas only 24% of children had a typical receptive-expressive phenotype (balanced profile). Language profiles were not concurrently associated with age, autism features, joint attention skills, motor or cognitive functioning. However, children with the EA profile at baseline showed significantly slower expressive language growth over 12 months than those with RA or balanced language profiles, suggesting that receptive-expressive language profiles may hold promise as early prognostic markers of expressive language growth in emerging autism.