Fragile-X and Down's syndrome: are there syndrome-specific cognitive profiles at low IQ levels?

Finney et al. (1995) compared kids with fragile-X and Down syndrome who all had very low IQs. They wanted to know if each syndrome has its own special thinking profile. The team gave the same set of IQ and memory tests to both groups.

When IQ is below 40, the two groups looked the same on every test. The kids’ scores lined up by IQ level, not by syndrome label. Genetic cause did not shape the profile—ability level did.

Wishart (1993) had already shown that Down kids lose skills and learn in fits and starts. W et al. add that this rocky path looks just like the fragile-X path when IQ is very low. Jänsch et al. (2014) later proved that facial features fool observers; real test scores, not looks, predict ability. Amore et al. (2011) seem to disagree—they found Down preschoolers imitate better than they talk. The key difference: M et al. studied single skills, while W et al. looked at the whole IQ profile. Taken together, the papers say: pick goals from test data, not from the syndrome name.

Stop writing separate Down or fragile-X programs for very low-IQ learners. Use the child’s tested mental age to set language, play, and self-care targets. One lesson plan fits both groups when IQ is under 40.