Long trial durations normalise the interference effect and sequential updating during healthy aging

• We examined age-related decrease in cognitive abilities using the Simon task.
• We observed larger congruency effect in seniors driven by greater interference.
• Seniors did not show Gratton sequential effect but it appeared with long durations.
• Seniors also showed decrease in interference effects with long trial durations.
• We conclude that aging may impair quick adaption strategies.

We examined the effect of a task-irrelevant dimension on response times in young adults and seniors. We used the Simon task with congruent trials where the target and manual response were on the same side, incongruent trials where the target and response were on opposite sides, and neutral trials where the target appeared along the vertical meridian. We observed two age-related effects. First, there was a larger congruency effect in senior participants that was driven by greater interference; namely, their responses were slower on incongruent relative to neutral trials. Second, there was a Gratton effect; namely, a diminished Simon effect was found in young adults but not in seniors when the preceding trial was incongruent. However, these effects of aging were normalised when the inter-trial interval was increased; the Simon effect and interference were reduced and a Gratton effect appeared for seniors. We conclude that aging may impair the ability to quickly adapt to changing environmental circumstances when they require reformulating current behavioral strategies.