Tower of Hanoi and working memory in adult persons with intellectual disability.

Firth et al. (2001) watched adults with intellectual disability solve the Tower of Hanoi puzzle. They paired each adult with a child who had the same fluid-intelligence score. The goal was to see if both groups solved the puzzle the same way.

The team counted rule breaks, extra moves, and trials needed to finish. They also tested visuo-spatial memory, executive working memory, and inhibition to learn which skills helped most.

Both groups finished the puzzle, but adults with ID broke rules more often and needed more tries. Even though their fluid-intelligence scores matched the children, their behavior on the task looked different.

Better inhibition, stronger visuo-spatial memory, and sharper executive working memory predicted fewer mistakes. Rule following, not just smarts, drove success.

Laugeson et al. (2014) pooled many studies and found medium-to-large inhibition deficits across people with ID. Firth et al. (2001) now shows those deficits matter on a real puzzle task, closing the loop between lab scores and everyday problem solving.

Bellon-Harn et al. (2020) also mental-age matched teens with ID to younger kids. Like H et al., they saw equal final scores but different learning paths. Together the papers argue that matching mental age hides process differences you still need to teach.

Cadette et al. (2016) warn that reaction-time tasks can be noisy in adults with ID. H et al. avoided this by using a hands-on puzzle, giving clearer data on executive skills.

When you test problem solving, watch rule compliance, not just correct answers. Adults with ID may need extra practice stopping impulsive moves. Build sessions that strengthen inhibition and working memory, like pause-and-plan drills or visual cues, before you teach multi-step tasks.