Domain general processes moderate age-related performance differences on the mnemonic similarity task.

Several prominent domain general theories (e.g., processing speed and inhibitory function) have been developed to explain cognitive changes associated with aging. A bias to "pattern complete" in aging has also been suggested to account for some of the age-related changes in episodic memory. The current experiments test whether domain-general processes of cognitive aging moderate age-related performance decrements on the mnemonic similarity task, a task thought to rely on hippocampal pattern separation and completion. The study phase of the mnemonic similarity task, a memory task with old, new, and similar trials at recognition, was manipulated to assess the contribution of processing speed (Experiment 1 - different encoding times) and inhibitory function (Experiment 2 - item-level directed forgetting) to age-related performance differences in a sample of 100 healthy younger and older adults. Both experiments exhibited significant interactions between age group and encoding manipulation, replicating a decrement in performance in older adults, and indicating that processing speed and inhibitory function moderate this effect. Results suggest that age-related differences in performance on the mnemonic similarity task can at least partially be accounted for by experimental manipulations of domain general processes that also decline with age.