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

Persons with intellectual disability (ID) have been found to perform more poorly than their mental age would suggest in the visuo-spatial problem solving task Tower of Hanoi (TOH). Inefficient performance has been assumed to be related to inability to use sophisticated problem solving strategies because of restricted working memory capacity. In the present study, the TOH performance of adult persons with ID was found to be equal to that of fluid-intelligence-matched general children. However, persons with ID violated the rules of the TOH more often, and needed more trials to solve the TOH problems than the children did. Visuo-spatial and executive working memory tasks were significantly connected to the TOH performance of persons with ID, whereas phonological working memory tasks were not. Poor inhibition ability was related to the poor performance of subjects with ID in the TOH. We suggest that for persons with ID, TOH performance is determined by individual differences in fluid intelligence, controlled attention, and inhibition ability.