Typically, subjective memory assessments (be it in form of single items or questionnaires) in old age only weakly correlate with the performance in objective memory tests at cross-section. It thus appears as if individual differences in subjective memory assessments hardly reflect individual differences in memory in old age. A shortcoming of cross-sectional studies, however, is that subjective assessments may rely on different individual standards, which are not taken into account. One solution to this problem has been to investigate subjective and objective memory longitudinally, thereby focusing on individual differences in intraindividual changes. Results from studies using this approach have been mixed, with some studies showing a significantly stronger relation between changes than between levels, and other studies showing no such significant difference. Using data from the Zurich Longitudinal Study on Cognitive Aging (n = 236), we find that 5-year changes in subjective assessments of memory capacity and memory changes correlate with objective memory changes of 0.54 and -0.44, respectively. These correlations are significantly stronger than at cross-section. After controlling for age, depressive affect, and subjective health at the first measurement occasion, correlations are slightly attenuated, but the basic findings remain the same.

The goal of the present study was to examine whether individual differences in basic cognitive abilities, processing speed, and working memory, are reliable predictors of individual differences in forgetting rates in old age. The sample for the present study comprised 364 participants aged between 65 and 80 years from the Zurich Longitudinal Study on Cognitive Aging. The impact of basic cognitive abilities on forgetting was analyzed by modeling working memory and processing speed as predictors of the amount of forgetting of 27 words, which had been learned across five trials. Forgetting was measured over a 30-minute interval by using parceling and a latent change model, in which the latent difference between recall performance after five learning trials and a delayed recall was modeled. Results implied reliable individual differences in forgetting. These individual differences in forgetting were strongly related to processing speed and working memory. Moreover, an age-related effect, which was significantly stronger for forgetting than for learning, emerged even after controlling effects of processing speed and working memory.

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The present study emphasized the role of analyzing individual differences in subjective organization. Implications are discussed, in particular, regarding the interdependency of subjective organization and verbal learning in old age.