Do age differences between young and older adults in inhibitory tasks depend on the degree of activation of information?

Three inhibition/interference tasks (Stroop colour, Negative priming embedded within the Stroop colour, and Hayling) were administered to young and older adults, with two main objectives, each of which embedded within a developmental perspective: First manipulate the level of activation of the irrelevant information, and second, assess the number of individuals presenting a reliable effect rather than analyse the results only at the group level. For each task, two versions were used, corresponding to two levels at which the irrelevant information was likely to be activated. Analyses were conducted on relative difference scores rather than on raw response times. Results indicated that age differences in the magnitude of an interference effect were small and even null in the Negative priming task, independently of the salience of the irrelevant information. A bootstrap procedure showed that whereas the majority of both young and older adults presented a reliable interference effect in the Stroop colour and in the Hayling tasks, it was not the case in the Negative priming task. Moreover, correlations between the indices of interference/inhibition were very weak questioning the dimensionality of inhibition. Altogether these findings suggest that highly activated versions of the inhibitory tasks used do not really influence age-related differences in inhibitory control. It is also recommended to use bootstrap procedures more frequently instead of restricting analyses at a group level.