Inhibition deficits in individuals with intellectual disability: a meta-regression analysis.
Expect large behavioral inhibition deficits in ID that shrink as IQ rises, while cognitive and motivational inhibition stay intact.
01Research in Context
What this study did
The team pooled 68 earlier experiments on inhibition in people with intellectual disability.
They used meta-regression to see if age, IQ, diagnosis mix, or task type changed the size of the inhibition gap.
All studies compared people with ID to typically developing peers on stop-signal, Stroop, or go/no-go tasks.
What they found
Behavioral and interference inhibition were clearly weaker in the ID groups; the gap was medium to large.
Cognitive inhibition and motivational inhibition looked normal.
Lower IQ made the deficit bigger, but age and extra diagnoses did not.
How this fits with other research
Firth et al. (2001) saw the same link in a single study: poor inhibition predicted extra moves and rule breaks on the Tower of Hanoi.
Cadette et al. (2016) later showed that reaction-time tasks can fail in mild ID because of high variability, echoing the need for clean measures.
Hagopian et al. (2005) and Matson et al. (2009) both tracked added diagnoses; they found worse symptoms or skills when autism or epilepsy joined ID, yet the meta-analysis found no extra hit to inhibition itself.
The papers do not clash: comorbidity may worsen daily skills or ADHD ratings, but the core inhibition deficit stays tied mainly to IQ level.
Why it matters
When you test a client with ID, pick tasks that tap behavioral or interference inhibition and expect bigger problems if IQ is below 55.
Do not assume extra labels like autism explain poor scores; look at IQ first.
For treatment, target stop-and-wait skills, not cognitive re-framing or motivation boosts, since those areas are intact.
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02At a glance
03Original abstract
BACKGROUND: Individuals with intellectual disabilities (ID) are characterised by inhibition deficits; however, the magnitude of these deficits is still subject to debate. This meta-analytic study therefore has two aims: first to assess the magnitude of inhibition deficits in ID, and second to investigate inhibition type, age, IQ and the presence/absence of comorbid problems as potential moderators of effect sizes. METHOD: Twenty-eight effect sizes comparing ID and age matched normal controls on inhibition tasks were included in a random effects meta-regression. Moderators were age, IQ, inhibition type and presence/absence of comorbid disorder. RESULTS: The analysis showed a medium to large inhibition deficit in ID. Inhibition type significantly moderated effect size, whereas age and comorbid disorder did not. IQ significantly moderated effect size indicating increasing effect size with decreasing IQ, but only in studies that included a sample of ID participants with mean IQ > 70. The analysis indicated comparable deficits in behavioural inhibition and interference control, but no significant deficits in cognitive inhibition and motivational inhibition. CONCLUSIONS: These results indicate that ID is characterised by a medium to large inhibition deficit in individuals with ID. ID seems not to be characterised by deficits in cognitive and motivational inhibition, which might indicate that distinct processes underlie distinct inhibition capacities.
Journal of intellectual disability research : JIDR, 2014 · doi:10.1111/jir.12068