Aging effects in response inhibition: general slowing without decline in inhibitory functioning

Previous research has examined aging effects on response inhibition using cognitive interference paradigms such as the Stroop task and the Simon task. Performance in these tasks requires participants to inhibit predominant responses. Reduced response inhibition is reflected by poorer performance in incongruent trials where prepotent responses can interfere with other correct responses, than in congruent trials without such interference (i.e., Stroop or Simon congruency effects). It is unclear whether such effects increase with normal aging. Balota et al. (2010) reported that the Stroop effect can be a useful predictor of conversion to Alzheimer's disease in a healthy control sample. Congruency effects are also subject to trial sequencing: They are smaller following an incongruent trial than following a congruent one. The present study determined whether response inhibition was affected by normal aging using the Simon task, with focus on the influence of normal aging on sequence effects. Forty-three young participants and 14 healthy elderly adults performed the Simon task individually. Results indicated that both age groups showed the same magnitude of Simon effects and sequence effects, although overall response latencies were longer in elderly participants than in young participants. Furthermore, the elderly adults tended to make fewer errors than the younger adults. These findings suggest that normal aging may produce reduced processing speed but it does not affect response inhibition itself.