Effects of instructed focus and task difficulty on concurrent walking and cognitive task performance in healthy young adults

Abstract

Dual task paradigms can be used to examine the interactions between cognition and the control of posture and gait. Measuring and interpreting changes in dual task performance is challenging, however, because many factors can influence performance. This study examined the effects of instructed focus and walking task difficulty, and the interaction between these factors, on dual task performance in healthy young adults. Fifteen participants performed a cognitive task while walking with either a usual base or a narrow base of support. Participants were instructed to focus on either the cognitive task or walking. Trade-offs both within and between tasks were assessed using the modified attention allocation index and the performance operating characteristic. Instructed focus influenced both the cognitive task and walking. Performance on the cognitive task was faster with instructions to focus on the cognitive task, and walking was faster (and more accurate in the narrow-base condition) with instructions to focus on walking. Walking task difficulty did not affect cognitive performance but did affect walking, with faster walking in the usual-base versus narrow-base condition. There was evidence of an interaction, with greater effects of instructed focus on the cognitive task during usual versus narrow-base walking. These results support the idea that the ability to flexibly shift attention allocation and task performance in response to instructions depends on the difficulty of the postural control task. The modified attention allocation index and the performance operating characteristic were instrumental in fully characterizing trade-offs between and within tasks in order to understand dual task performance changes. A clearer understanding of the factors that affect dual task walking and the interactions between these factors has important implications for the assessment of dual task performance in both clinical and research settings.

Fig. 1

The effect of instructed focus and walking task difficulty on cognitive task response latency (a) and response accuracy (b). Symbols represent means for cognitive task performance in the single task (ST) condition (diamonds) and under usual-base (squares) and narrow-base (triangles) walking dual task conditions. Bars represent standard errors (note standard errors for response accuracy were <1% in all cases). ST single task condition, walk focus walking focus condition, cog focus cognitive task focus condition

Fig. 2

The effect of instructed focus and walking task difficulty on usual and narrow-base gait speed (a), and the effect of instructed focus on narrow-base step accuracy (b). Symbols represent means for walking under usual-base (squares) and narrow-base (triangles) walking conditions. Bars represent standard errors. ST single task condition, walk focus walking focus condition, cog focus cognitive task focus condition

Fig. 3

Modified attention allocation index (mAAI) values to examine within-task trade-offs in response to instructions for each individual. Cognitive task (response latency and response accuracy) mAAI values under usual-base and narrow-base walking conditions (a). In response to instructions to focus on walking versus the cognitive task, participants primarily decreased response latency, with minimal changes in response accuracy. Walking (gait speed and step accuracy) mAAI values under the narrow-base condition (b). In response to instructions to focus on walking versus the cognitive task, participants showed a variety of within-task trade-offs. Some participants increased step accuracy and decreased gait speed, some decreased step accuracy and increased gait speed, and some increased both gait speed and step accuracy

Fig. 4

Performance operating characteristic framework showing the effects of instructed focus and task difficulty. Single task performance is represented by the dashed lines. The dual task effects for each point are reflected in the distance from each point to the line representing single task performance. Points represent means and bars represent standard errors (note standard errors for UB walking ≤1% in both cases)