A recent study by Ben-David et al. (2014) indicated that older adults process redundant targets with a larger workload capacity than younger adults, even though older adults exhibit generally slower response times (RTs). To investigate the organization of mental processes that underlie age-related differences, we conducted four experiments with redundant-target tasks. In a series of discrimination-type redundant-target tasks (Experiments 1–3), we replicated the age-related capacity advantage; however, the differences were eliminated in a detection-type redundant-target task (Experiment 4). Our results supported the distractor inhibition account, which suggests that age-related differences were due to less efficiency in attentional control to resolve the response conflict when making discrimination decisions. Moreover, we conducted a simulation using a Poisson parallel interactive model, which assumes an inhibitory interaction between two parallel channels that is a result of a limited attentional capacity. An analysis of the model's predictions indicated the two key findings that may account for the age-related capacity differences: the older adults (1) processed the redundant targets with a higher decision criterion (i.e., more conservative in decision-making) and (2) exhibited a greater violation of context invariance (i.e., less degree of controlled attention in dealing with the response conflict). The extensive modeling analyses highlighted the effect of a decline in attentional control on age-related differences in workload capacity.
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