Age effects on category learning and their relationship to deficits in memory specificity

Age deficits in memory for individual episodes are well established. Less is known about how age affects another key memory function: the ability to form new conceptual knowledge. Here we studied age differences in concept formation in a category-learning paradigm with face-blend stimuli, using several metrics: direct learning of category members presented during training, generalization of category labels to new examples, and shifts in perceived similarity between category members that often follow category learning. Age deficits in categorization were compared to metrics of memory specificity (recognition, cued-recall) for the same set of stimuli. We found that older adults were impaired in direct learning of training examples, but there was no generalization deficit above-and-beyond the deficit in direct learning. We also found that category learning affected the perceived similarity between members of the same versus opposing categories, and age did not significantly moderate this effect. When comparing categorization to memory specificity, we found that categorization deficits were smaller than deficits in recall and comparable to deficits in recognition, showing that categorization deficits are smaller than some of the largest known age-related memory deficits. Lastly, we compared traditional category learning to categorization after a learning task in which a category label (shared last name) was presented alongside stimulus-specific information (unique first names that individuated category members). We found that simultaneously learning stimulus-specific and category information resulted in decreased category learning in both age groups, and that this decrement was not disproportionate in older adults.