Cognitive development and Down syndrome: age-related change on the Stanford-Binet test (fourth edition).

Couzens et al. (2011) followed people with Down syndrome for many years. They gave the Stanford-Binet IQ test again and again to see which skills grow and which stall.

The team tracked four kinds of tasks: repeating sentences, solving picture puzzles, naming pictures, and answering why questions.

Every person had a different path. Some kids zoomed ahead; others stayed flat.

Sentence memory barely moved after age ten. Puzzle solving kept climbing into the twenties. Word and why tasks rose fast at first, then hit a low ceiling.

Channell et al. (2014) saw the same flat standard scores in teens, but raw puzzle scores still inched up. Their data echo Donna’s puzzle rise and sentence stall.

Sharp et al. (2010) found daily-living skills plateau around twelve. Donna’s language scores also plateau early. Together they map a double ceiling: thinking and living skills.

Alaimo et al. (2015) later showed that after thirty, adults use fewer adaptive skills, not worse skills. Donna ends at thirty, so T extends the story: the ceiling stays, then the floor shrinks.

Stop waiting for language-heavy scores to rise. Shift goals to practical puzzles and daily routines once words level off. Track raw counts, not IQ numbers, to show real gains parents can see.