Transfer and interference of motor skills in people with intellectual disability.
People with ID need separate practice for each hand and extra support when a second task is added.
01Research in Context
What this study did
The team asked adults with intellectual disability to learn a simple hand task.
They then tested how well the skill moved to the other hand and how it held up when a second task was added.
A comparison group without disability did the same drills.
What they found
Skill moved poorly from the non-dominant to the dominant hand in the ID group.
Adding a second task hurt their performance more than it hurt the control group.
Oddly, both groups did slightly better with the non-preferred hand.
How this fits with other research
Josseron et al. (2025) saw a similar road-block: kids with Developmental Coordination Disorder also struggle to move a motor skill to a new place.
Merrill (2004) used a visual search duel task and got a mixed picture, yet still showed people with ID bog down when two jobs run at once.
Hung et al. (2011) flipped the coin: intensive two-hand training improved coordination in kids with hemiplegia, showing practice can beat the transfer problem if you target both limbs together.
Why it matters
For your clients with ID, do not assume that teaching one hand will automatically help the other.
Plan extra trials for the second hand and keep the room quiet while they work.
If you must add a verbal or counting task, cut the motor demand first so the skill stays solid.
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02At a glance
03Original abstract
Atypical laterality (i.e. the lack of a clear pattern of lateralization) has been found to be a characteristic feature of individuals with intellectual disability (ID). The evidence for this has been based on 'handedness' studies which have contained little information about the ability of people with ID to carry out interhemispheric tasks reflecting bilateral transfer or interference. The present study examined this capacity in individuals with ID by utilizing bilateral transfer and interference paradigms. Right-handed subjects with ID (IQ = 55-76) and controls matched for age and sex were tested for bilateral transfer of motor skill in contralateral hands with a mirror-drawing task. The subjects were also tested for their ability to perform a finger-tapping task while processing verbal and non-verbal stimuli. The findings indicated that people with ID are significantly deficient relative to matched controls in bilateral transfer of motor skills from their non-preferred (left) hand to their preferred (right) one. The effect of interference during performance of the dual task was significantly greater in individuals with ID. Subjects with ID were found to perform better with their non-preferred than with their preferred hand. A within-group comparison revealed that right-handed performance was more affected by interference than left in these subjects.
Journal of intellectual disability research : JIDR, 2001 · doi:10.1046/j.1365-2788.2001.00341.x