Effects of Orthographic, Morphological and Semantic Overlap on Short-Term Memory for Words in Typical and Atypical Development

Little is known about implicit morphological processing in typical and atypical readers. These studies investigate this using a probe detection task with lures sharing morphological, orthographic, or semantic overlap with the probe. Intermediate and advanced readers (reading ages = 9;1–12;9) perform more poorly when there is more linguistic overlap. Novice readers (reading ages = 5;7–8;0) were influenced only by orthographic overlap and not by semantics, indicating that use of orthographic processes typically precedes integration of semantic and morphological skills. Children with otitis media (repeated ear infections) had phonological awareness difficulties but performed age appropriately on the probe detection task, indicating that morphological processing is not constrained by phonology. In contrast, dyslexic children’s performance reflected a failure to remember distinctions between words sharing root morphemes. Dyslexic children are sensitive to morphology but may over-rely on root morphemes. This pattern differed from reading-ability-matched children and children with circumscribed phonological difficulties.