Ulrich Mayr, Reinhold Kliegl

• Dimensions of cognitive complexity in figural transformations were examined in the context of adult age differences. Sequential complexity was manipulated through figural transformations of single objects in a multiple-object array. Coordinative complexity was induced through spatial or nonspatial transformations of the entire array. Results confirmed the prediction that age-related slowing is larger in coordinative complexity than in sequential complexity conditions. The effect was stable across 8 sessions (Experiment 1), was obtained when age groups were equated in accuracy with criterion-referenced testing (Experiment 2), and was corroborated by age-differential probabilities of error types (Experiments 1 and 2). A model is proposed attributing age effects under coordinative complexity to 2 factors: (a) basic-level slowing and (b) time-consuming reiterations through the processing sequence due to age-related working memory failures.