Walking (and talking) the plank: Dual-task performance costs in a virtual balance-threatening environment

We evaluated the effects of engaging in extemporaneous speech while walking in virtual environments meant to elicit low or high levels of mobility-related anxiety. We expected that mobility-related anxiety imposed by a simulated balance threat (i.e. virtual high elevation) would impair walking behavior and lead to greater dual-task costs. Altogether, 15 adults (age = 25.6 {+/-} 4.7 yrs, 7 women) walked at their self-selected speed within low (ground) and high elevation (15 meters) VR settings while speaking extemporaneously (dual-task) or not speaking (single-task). Likert-scale ratings of cognitive and somatic anxiety, confidence, and mental effort were evaluated after experiencing each condition, and gait speed, step length, and step width, and the variability of each, was calculated for each trial using the position of trackers attached to participants ankles. Silent speech pauses (>150ms) were determined from audio recordings to infer the cognitive costs of extemporaneous speech planning at low and high virtual elevation. The presence of a balance threat and the inclusion of a concurrent speech task both perturbed gait kinematics, but only the virtual height illusion increased anxiety and mental effort while decreasing confidence. Extemporaneous speech pauses were longer on average when walking, but no effects of virtual elevation were reported. Trends toward interaction effects arose in self-reported responses, participants reported more comfort walking at virtual heights if they engaged in extemporaneous speech. Walking at virtual elevation and walking while talking have independent and significant effects on gait; both effects were robust and did not support an interaction when combined (i.e., walking and talking at virtual heights). Rather than additive cognitive-motor demands, the nature of extemporaneous speech may have distracted participants from the detrimental effects of walking in anxiety-inducing settings.