Cognitive abilities in old age: Results from the Zurich Longitudinal Study on Cognitive Aging

The Zurich Longitudinal Study on Cognitive Aging (ZULU) is an ongoing longitudinal study on the structure and development of cognition in old age. At the first assessment, the N = 364 participants had an average age of 73 years (age range: 65-80 years), and 46% were female. In total a battery of 14 cognitive tests. including five consecutive verbal learning trials, were administered and adequately described by a measurement model of six first-order factors (processing speed, working memory, reasoning, learning, memory, and verbal knowledge) and one Second-order factor of general cognitive ability. The cross-sectional age relations of the six cognitive abilities were, apart from processing speed and verbal knowledge, mediated by the general cognitive ability factor. From a conceptual perspective, these results imply that cognitive aging is not a completely uniform process driven by a single causal variable.