In the present study, it was proposed to investigate the effects of aging on the strategies used to solve a block design task and to establish whether these strategies may be associated with differential patterns of ability. Two groups of subjects, 30 young adults (aged 20-35 years) and 30 middle-aged adults (aged 45-60 years) were set a computer version of the Kohs task and a battery of tests. An age-related decrease in fluid intelligence (Gf) and visual-spatial ability (Gv) was observed, along with the fact that most of the older subjects used a global strategy rather than a synthetic one. On the other hand, while continuing to use strategies of the analytic type, the older subjects looked more frequently at the model and scored high on crystallized intelligence (Gc). These findings are discussed from two different points of view: the theory of hierarchical stimuli and the hypothesis that metacognitive ability, which is thought to rely on Gc, may increase with age, and thus compensate for the loss of Gf and Gv.