Inhibitory control over the present and the past

From the perspective of the Hasher, Zacks, and May (1999) inhibitory framew ork, optimal performance occurs only when there is control over nonrelevant information. Relative to a current, goal-directed task, there are at least two potential sources of nonrelevant information that need to be controlle d. The first is no longer relevant information. Such information would incl ude, for example, a previous topic of conversation, or, in our work, a prev ious list of materials presented for study and recall. The second source of nonrelevant information is currently present (in thought or in the world) stimuli that are not relevant to the task at hand. Inhibitory processes are critical to the effective control of both sources of information-the no lo nger relevant past and the irrelevant present. If inhibitory processes are inefficient, irrelevant information from both the past and the present will disrupt performance on the current task. We illustrate this with studies s howing the role of irrelevant information in reducing the working memory ca pacity of older adults and in slowing them down as they do even reasonably simple tasks.