Excess of non-right handedness among individuals with intellectual disability: experimental evidence and possible explanations.

Schlundt et al. (1999) counted how many adults with mild or moderate intellectual disability used their left hand for everyday tasks.

They compared the count to adults without disability who were the same age and sex.

A quick handedness checklist was the only tool; no therapy was tested.

More people with ID favored the left hand than the control group.

The authors say this may point to unusual brain wiring, but they did not test brain scans.

Oppewal et al. (2013) later used the same handedness fact to show grip strength can be weaker on the "dominant" side in older adults with ID.

Because of that, they tell us to test both hands, not just the one the client writes with.

Sandberg et al. (2026) widened the lens with a giant registry and found higher rates of almost every diagnosis in people with ID, giving the left-hand clue a place in a bigger health map.

The 1999 paper sits early in this chain: it flags a simple marker that later studies turn into practical advice.

When you do an intake, note which hand the client prefers. It will not change your program, but it reminds you that this learner may have other atypical wiring. Pair this with Alyt’s tip: if you ever test grip or fine-motor skill, check both hands. One quick line in your file keeps your data clean and your goals fair.