Depth of processing and the negative priming effect : age differences in inhibitory functioning

The hypothesis that older adults have more difficulty than younger adults suppressing irrelevant information has been both supported and refuted by past research. The 'gold standard' for measuring inhibitory functioning is the negative priming paradigm. This study examined variables that might help explicate the contradictory findings from past research with this paradigm with the goal of understanding better the age changes in attentional processes. In Experiment 1, 31 young and 31 older adults were tested under three negative priming procedures, considered to require different depths of processing. Older adults did not show inhibition in the low processing procedure but did in the other two procedures while younger adults showed inhibition in all three tasks. The inhibition effect for older adults exceeded that for the young in the task requiring the deepest level of processing. In Experiment 2, 87 older adults, classified as Low, Mid or High in level of Off-target verbosity, believed to be associated with inhibitory deficits, were tested on the same tasks. As in Experiment 1, older adults did not show an inhibition effect in the low processing procedure but did show an effect in the other two procedures. In addition, the inhibition effect for those in the highest group was greater than for the other groups in the deepest processing task. In Experiment 3, 50 young adults and 49 older adults were administered a new negative priming procedure. Level of processing was manipulated in two ways. One manipulation resulted in equal inhibition effects for both age groups and the other resulted in a greater effect for older adults than for younger adults. The results from these experiments support the notion that depth of processing is related to the extent to which older adults will show an inhibitory effect and that requiring greater depths of processing may result in excess inhibition as opposed to a reduction in inhibition. Discussions include an attempt to integrate both the inhibition and the episodic retrieval models. Recommendations include a need for a reevaluation of the negative priming paradigm and for examining the association between different brain functions and different inhibitory functions