Abilities underlying decoding differences in children with intellectual disability.
For kids with ID, phonological rehearsal beats IQ as a reading predictor, so target sound memory first.
01Research in Context
What this study did
The team compared kids with intellectual disability who were strong readers to those who were weak readers. They looked at IQ scores, language skills, and phonological rehearsal. Phonological rehearsal is the silent loop in your head that keeps sounds ready while you read.
What they found
After holding age constant, only phonological rehearsal split the strong and weak decoders. IQ and language scores did not matter. In short, the kids who could hold sounds in mind read better, no matter their overall IQ.
How this fits with other research
Levy (2011) seems to say the opposite: in teens with ID, IQ fully explains the link between phonological skills and decoding. The gap is age. Cullinan et al. (2001) tested children; Yonata tested adolescents. IQ may gate reading later, but not at first.
Van der Molen et al. (2010) reviewed 20 Down-syndrome studies and found phonological awareness helps reading there too. The new detail here: rehearsal, not awareness, is the key within pure ID.
Critten et al. (2019) saw the same pattern in kids with cerebral palsy: weak phonological and visual memory predicted reading delay. The message across disabilities: check the memory loop early.
Why it matters
Stop waiting for a minimum IQ before you teach phonics. If a child with ID can repeat three spoken sounds, start decoding lessons and track progress. Use brief sound-span games to build that loop. Rehearsal is teachable; IQ is not.
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02At a glance
03Original abstract
Researchers in recent years have made much progress towards understanding why some children struggle to learn to read. However, little of this research has involved children with intellectual disability associated with an IQ < 70 (ID, also called mental retardation). In the present analysis, the authors examined cognitive similarities and differences between stronger and weaker decoders, all of whom have ID. The 65 children with ID in the present analysis were initially referred by their teachers for a study that involved training basic phonological reading skills. The present analysis compares 21 children who were excluded from the training study because their decoding skills were already too high with 44 children whose decoding skills were low enough for the training study. The groups were compared on general intelligence, language ability, phonemic awareness and phonological memory. Initial analyses showed that the stronger decoders were significantly better than weaker decoders in language ability, phonemic awareness and rehearsal in phonological memory, but not in intelligence. They were also significantly older than weaker decoders. When age was covaried out, the groups differed significantly only in rehearsal in phonological memory, although the difference for phonemic awareness was marginally significant when the poorest performers were excluded. When intelligence is substantially limited, the ability to rehearse or refresh phonological codes in working memory plays a major role in determining children's success in learning to read. This ability appears to be more important than intelligence, language ability and phonemic awareness. It is possible that the reason the phonemic awareness measure was not as good at distinguishing the groups as the phonological rehearsal measure was because the former did not involve assembling phonological output. It is suggested that it is the combination of poor phonological representation and poor phonological output assembly that makes decoding difficult for some children with ID.
Journal of intellectual disability research : JIDR, 2001 · doi:10.1046/j.1365-2788.2001.00319.x