Mechanisms underlying the age-related changes in discrete manual aiming

Abstract

Age has a clear impact on one’s ability to make accurate aiming movements. As a result, older adults typically slow down their initial pulse towards the target, and spend more time making corrections. Despite these age-related changes have been observed consistently, their underlying mechanism remains speculative. In this study, young (19 – 25 years old) and older (60 – 71 years old) adults were asked to aim as fast and accurate as possible towards a target (index of difficulty: 6.2). Afterwards, several aiming conditions were presented in which one of four commonly referred causes was isolated. First, when aiming without accuracy constraints, older adults demonstrated similar movement speeds as young controls (p > .05), indicating the changes are not caused by a physical inability to generate high muscle forces. Second, as the temporal and spatial variability of three kinematic markers did not differ among groups (p > .05), evidence for an age-related increase in noise-to-force ratio was not found either. Third, older adults needed more time to verify the movement had ended (p < .01), implying an age-related decrease in feedback-processing efficiency. Finally, evidence for older adults adopting a play-it-safe strategy was found: when the cost of a target overshoot was increased, young adults’ aiming movement suddenly demonstrated several characteristics typically linked with older adults (p < .05). The results of this study suggest that the age-related changes in manual aiming are caused by older adults’ decreased efficiency in feedback processing and their implementation of a play-it-safe strategy.