Stepping into recalibration: an exploration of age-related effects

In the United Kingdom, about a third of adults aged over 65 years fall each year (Public Health England, 2018). In older age, recalibration is thought to be necessary to cope with acute and long-term changes within the perceptual and musculoskeletal systems. Recalibration is the rescaling of the perceptual-motor system, which happens after there is a disturbance to the system (Franchak, 2017; Withagen & Michaels, 2004). However, it is possible that recalibration is affected by older age, thereby slowing down the negotiation of actions in new contexts, which could potentially lead to falls in older adults. A systematic review of the literature showed that while young adults recalibrated relatively fast to disturbances to the perceptual-motor system, no research had yet focused on recalibration in older adults. Therefore, the aim of this thesis was to explore whether there are age-related effects in the recalibration to action disturbances. The systematic review also showed the importance of investigating the timeframe of recalibration using a trial-by-trial analysis of the rearrangement process. In the first study, we investigated age-related differences in the recalibration of their affordance perception after disturbing their action boundaries. No recalibration was found in this judgement study, which also showed that the availability of relevant information was essential for recalibration to occur. The two subsequent studies investigated perceptual-motor everyday activities, stair climbing and obstacle crossing, using kinematic measures. An innovative methodology was applied, which identified the timeline of recalibration as the point where a stable movement pattern emerged. By investigating everyday activities, we found that both young and older adults recalibrated quickly, albeit not in the same way. Age-related differences showed that young adults recalibrated faster than older adults in a predictable environment (climbing stairs of a fixed height), but the young adults recalibrated slower when faced with an unpredictable environment (crossing obstacles of varying heights). It seems that the process of recalibration was intact in both groups, but recalibration speed may have been constrained by reduced action capabilities and perceived consequences of the task in the older group. These findings have broader theoretical and practical implications for future research in recalibration.