Gazing into Thin Air: The Dual-Task Costs of Movement Planning and Execution during Adaptive Gait

Abstract

We examined the effect of increased cognitive load on visual search behavior and measures of gait performance during locomotion. Also, we investigated how personality traits, specifically the propensity to consciously control or monitor movements (trait movement ‘reinvestment’), impacted the ability to maintain effective gaze under conditions of cognitive load. Healthy young adults traversed a novel adaptive walking path while performing a secondary serial subtraction task. Performance was assessed using correct responses to the cognitive task, gaze behavior, stepping accuracy, and time to complete the walking task. When walking while simultaneously carrying out the secondary serial subtraction task, participants visually fixated on task-irrelevant areas ‘outside’ the walking path more often and for longer durations of time, and fixated on task-relevant areas ‘inside’ the walkway for shorter durations. These changes were most pronounced in high-trait-reinvesters. We speculate that reinvestment-related processes placed an additional cognitive demand upon working memory. These increased task-irrelevant ‘outside’ fixations were accompanied by slower completion rates on the walking task and greater gross stepping errors. Findings suggest that attention is important for the maintenance of effective gaze behaviors, supporting previous claims that the maladaptive changes in visual search observed in high-risk older adults may be a consequence of inefficiencies in attentional processing. Identifying the underlying attentional processes that disrupt effective gaze behaviour during locomotion is an essential step in the development of rehabilitation, with this information allowing for the emergence of interventions that reduce the risk of falling.

The influence of anxiety and attentional focus on visual search during adaptive gait.

“…A second aim of Experiment 2 was to explore the possible mechanisms through which adopting an internal focus of attention may alter visual search during locomotion. For example, consciously attending to movement during locomotion has been shown to reduce processing efficiency, thus limiting the resources available for processing concurrent tasks (Ellmers & Young, 2018;Young et al, 2016)-which may include extracting relevant visual information from one's walking environment (Uiga et al, 2015b). Indeed, researchers (e.g., have proposed reduced cognitive resources as one possible explanation for restricted visual previewing and subsequent premature transfers of gaze.…”

“…As such, while we attribute the majority of changes observed in Experiment 1 to altered (on-line visual) prioritisation resulting from attempts to consciously process movement-rather than associated reductions in processing resources-we regardless deemed it necessary to also consider (and discount) the influence of reduced attentional resources available for movement planning on visual search during gait. Given that an internal focus of attention during locomotion is associated with verbal processes (Young et al, 2016), this was achieved through the manipulation of a verbal dual-task. However, we predicted to observe significantly different visual behaviours during this condition compared to Internal focus of attention (and a lack of any behaviours comparable to Threat in Experiment 1).…”

“…Identical gaze behaviour variables were also calculated, with the exception of an additional fifth walkway area: 'outside areas' (any area of the surrounding environment that was not along the walking path). Based on previous research (Ellmers et al, 2016), this additional area was added to assess the degree to which participants 'disengaged' from visual search during Cognitive dual-task. As with Experiment 1, trials in which the point of gaze crosshair disappeared for the duration of three frames or more were discarded.…”

“…In contrast, researchers have also utilised self-focus theories to explain how fall-related anxiety may alter visual search during gait (Uiga, Cheng, Wilson, Masters, & Capio, 2015b;. Evidence exists for a causal link between fall-related anxiety and heightened conscious movement processing when walking (Ellmers & Young, 2018;Young et al, 2016). As this form of movement execution is characterised by increased on-line movement processing (Jackson, Ashford, & Norsworthy, 2006), it is possible that the reduced visual exploration observed in anxious individualswhereby gaze is fixated predominantly on the "ground nearby in the heading direction" (Kugler et al, 2014, pp.…”

“…The same 14 participants from Experiment 1 participated in Experiment 2. As we wished to explore the potential factors underpinning the specific anxiety-related changes observed in Experiment 1, we deemed it most appropriate to utilise the same sample previously studied, rather than recruiting a new sample who may differ on trait variables likely to influence visual search during gait (such as an individual's trait propensity to consciously process their movements; Ellmers et al, 2016). To ensure an absence of a practice effect occurring during the testing session, separate paired-samples t-tests/Wilcoxin tests (dependent on whether the data were normally distributed) were used to compare Baseline variables between the two experiments.…”