Cognitive flexibility among individuals with Down syndrome: assessing the influence of verbal and nonverbal abilities.

Campbell et al. (2013) gave 22 people with Down syndrome a flexible-thinking test called the FIST.

They also gave two short IQ-style tests: one for words and one for puzzles.

The team asked which IQ score better predicted flexible-thinking success.

Only the verbal score mattered.

Higher verbal mental age went with higher flexibility scores.

The puzzle score added no useful information.

Soltani et al. (2022) later showed the same link in a larger youth sample.

They found executive skills, not just vocabulary, drive verbal fluency in Down syndrome.

Sandkühler et al. (2025) built a picture-based flexibility test so reading is no longer needed.

Their Dice Trails Test now lets you measure the same skill without verbal demands.

Together the three papers say: verbal ability predicts flexibility, yet you can still test flexibility without words.

When you assess a client with Down syndrome, start with verbal level.

If verbal skills are low, pick a nonverbal flexibility tool like Dice Trails.

This one switch gives cleaner data and avoids false delay labels.