Phonological short-term memory impairment and the word length effect in children with intellectual disabilities.
Kids with mild ID show a weaker word-length effect because they don’t rehearse—so teach rehearsal outright.
01Research in Context
What this study did
Sebastian’s team tested the kids with mild intellectual disability and 36 mental-age matches. All kids tried to repeat lists of short words and long words. The lists got longer until the child failed.
They tracked how many words each group recalled and where in the list mistakes happened.
What they found
Typical kids remembered more short words than long words—the classic word-length effect. Kids with ID showed a much smaller gap, and only at the end of the list.
The weak effect tells us these children do not silently repeat, or rehearse, the words to themselves.
How this fits with other research
Xie et al. (2024) extends this idea. They gave children with ID a memory strategy—acting out the instructions. Enactment helped, but the gain was smaller than for typical peers. Both papers agree: rehearsal skills are under-developed in ID.
Helland et al. (2014) looked at a different group—kids with behavior problems—and found lasting pragmatic language deficits. Their work reminds us that language trouble can come from many places, not just weak phonological memory.
Đorđević et al. (2016) studied adults with ID and showed that even within ID, severity matters. Together these studies warn us not to treat “ID” as one block; drill down to the specific skill.
Why it matters
If a child with ID fails memory tasks, do not assume the whole system is broken. Target the missing piece—subvocal rehearsal. Teach the child to whisper or mouth the words while holding them. Start with short lists and give clear rehearsal cues. This small shift can widen the gap between short- and long-word recall and boost overall language learning.
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02At a glance
03Original abstract
There is mounting evidence that children and adolescents with intellectual disabilities (ID) of nonspecific aetiology perform poorer on phonological short-term memory tasks than children matched for mental age indicating a structural deficit in a process contributing to short-term recall of verbal material. One explanation is that children with ID of nonspecific aetiology do not activate subvocal rehearsal to refresh degrading memory traces. However, existing research concerning this explanation is inconclusive since studies focussing on the word length effect (WLE) as indicator of rehearsal have revealed inconsistent results for samples with ID and because in several existing studies, it is unclear whether the WLE was caused by rehearsal or merely appeared during output of the responses. We assumed that in children with ID only output delays produce a small WLE while in typically developing 6- to 8-year-olds rehearsal and output contribute to the WLE. From this assumption we derived several predictions that were tested in an experiment including 34 children with mild or borderline ID and 34 typically developing children matched for mental age (MA). As predicted, results revealed a small but significant WLE for children with ID that was significantly smaller than the WLE in the control group. Additionally, for children with ID, a WLE was not found for the first word of each trial but the effect emerged only in later serial positions. The findings corroborate the notion that in children with ID subvocal rehearsal does not develop in line with their mental age and provide a potential explanation for the inconsistent results on the WLE in children with ID.
Research in developmental disabilities, 2014 · doi:10.1016/j.ridd.2013.11.025