In this study, and while using a VR paradigm, we showed that facial masks affect pedestrian circumvention when walking in a community environment. We further showed that obstacle clearance outcomes were associated with the level of anxiety but not the frequency of community ambulation in the context of the COVID-19 pandemic. Possible explanations and implications of these findings are presented below.
From all metrics describing obstacle circumvention, onset distance was the only outcome that changed significantly when the VRPs were wearing a facial mask. Indeed, when participants avoided an approaching VRP that was not wearing a facial mask, trajectory deviations started on average at 2.64m from the VRP. This anteroposterior distance reflects the point at which pedestrians begin to adapt their walking trajectory in response to an obstruction and its magnitude indicates a critical point at which walking adaptations are deemed necessary to smoothly and safely avoid collisions 21. In the current experiment, when the approaching VRP wore a facial mask, this onset distance was increased by approximately 0.18m. This change in onset distance is, in our perspective, meaningful, as unlike other obstacle clearance metrics such as minimum distance and maximum deviation, onset distance is a fairly stable measure that was shown to remain constant despite manipulations of characteristics of the interferer, such as gender, size, body orientation, and pattern of limb movements 7,26.
Modulations in this onset distance have been reported, however, according to the direction of obstacle approach (Buhler & Lamontagne, 2018; Souza Silva et al., 2018). In the present study, as well as in previous investigations, onset distance was found to be enlarged in response to head-on approaching pedestrians. This increase in the anteroposterior clearance may reflect the execution of a safer strategy that is used in conditions involving a greater risk of collision. Likewise, in the context of this study, which was conducted during the pandemic, it is also possible that observing a VRP wearing a facial mask would make participants more aware of an infection risk. Consequentially, a larger onset distance would allow participants to move away, at a greater distance, from the direction at which the VRP would be exhaling. At this distance, they would be less likely to be in contact with respiratory droplets that could lead to a COVID-19 infection. Considering the results of a recent survey where masked individuals were perceived to prefer larger interpersonal distances 16, it is also possible that participants may have perceived the VRPs wearing a mask in the same fashion, resulting in an increased onset distance.
Results also show that other measures of obstacle clearance (i.e., minimum distance and maximum deviation) did not differ between the mask vs. no mask conditions. There was, however, a trend towards larger clearances in the mask condition which can be clearly observed in the bar graphs presented in Fig. 4. This observation, combined with the onset distance results discussed above, further highlights how wearing a facial mask in the context of the COVID-19 pandemic influences interpersonal distances. Interestingly, while we expected that longer fixations on the approaching interferer would be maintained in the mask condition, especially on the interferer’s head, such an effect was not observed. It is possible that a short fixation on the interferer’s head provided sufficient information to bring about changes in obstacle circumvention strategies. The fact that trials where the interferer was wearing a mask were performed in sequence and that other pedestrians in the environment were also wearing a mask may have also minimized the need to visually scan for the presence of a facial mask. Importantly, the fact that a mask-induced effect could be detected in this study adds further support to the use of VR as a valid tool to study movement behavior in the context of social interactions. In previous studies from our laboratory, and even though VR can introduce a distance perception bias (Renner et al., 2013), we have shown that obstacle avoidance behavior is essentially the same in response to virtual vs. real pedestrians, with similar onset distance values and slightly larger minimum distances in VR (Buhler & Lamontagne, 2018, 2019). It is thus reasonable to assume that the mask-induced changes observed in the present study do reflect a natural behaviour. It cannot be fully excluded, however, that the effects due to the facial mask might be even larger in the physical world where the contamination risk is ‘real’, especially since 63% of participants reported feeling less anxious when interacting with the VRPs compared to real pedestrians.
The healthy and young participants tested as part of this study reported a low frequency of community walking during and after the confinement period. Considering the confinement measures that were put in place and the high adherence to these measures that our participants reported, this finding was not unexpected. Interestingly, after the confinement period, the frequency of community ambulation increased but only by a small amount. In agreement with a recent study that compiled mobile device data from 1.62 million anonymous users in 10 metropolitan areas in the United States 27, results from our questionnaire suggest that while community ambulation increased with the easing of lockdown restrictions, people still show signs of reluctance to leave their homes.
Overall, participants were somewhat anxious towards community ambulation. In parallel, they reported maintaining larger interpersonal distances when interacting with another pedestrian after the pandemic started. These observations show that the pandemic and confinement measures influenced self-reported psychological and behavioral metrics related to community ambulation. In addition, we observed strong positive correlations between anxiety and clearance measures during actual obstacle avoidance while walking. These findings corroborate a previous study that showed associations between anxiety and a preference for larger interpersonal distances 19. Furthermore, the stronger and more consistent (i.e., present for the mask and no-mask conditions) correlations observed between anxiety and onset distance (vs. minimum distance) supports the idea that modulations of the anteroposterior interpersonal distance are implemented as an infection prevention strategy. Taken together, results show that in the context of the pandemic, anxiety towards community ambulation is associated with larger clearances during pedestrian circumvention, which is reflected primarily by an enlargement of anteroposterior interpersonal distances. Furthermore, our findings provide additional evidence that factors beyond sensorimotor processes, such as social context and psychological status, influence complex behaviors such as pedestrian interactions.
All locomotor measures of obstacle circumvention, excluding maximum walking speed and fixation on the head of the approaching VRP, differed significantly according to the direction from which the VRP approached. These variations in circumvention strategies for most have been previously observed 9,24,25,28 and appear to reflect adaptations according to the bearing angle 10 or whether the pedestrian passes in front of behind the VRP 12.
In the context of this experiment, the right and left obstacle approach conditions represent the same bearing angle of 30° and the middle condition represents a bearing angle of 0°. With respect to the role taken by the participant during the task, while diagonal approaches represent an unresolved situation where they can decide to pass in front or to give-way, the middle condition requires the participant to give way (Olivier et al., 2013). Accordingly, all measures of obstacle clearance (i.e., minimum distance, maximum deviation, and onset distance) showed significant differences between the diagonal obstacle approaches (left or right) and the middle approach, while no differences were observed between the diagonal obstacle approaches. In the middle condition, the observation of larger deviations that started at greater distances from the VRP, yet still resulting in smaller minimum clearances, suggests a higher degree of challenge when compared to the diagonal conditions.
When considering gaze fixation outcomes, differences between the direction of interferer approach were also observed. As depicted in Fig. 4, in the middle condition, participants maintained longer fixations on the approaching VRP and shorter fixations on the other VRPs. Interestingly, the opposite pattern was observed in the diagonal approach conditions. These findings suggest that rather than fixating their gaze on the approaching interferer, participants were likely looking straight ahead, that is towards their heading direction and/or target. Lastly, we observed larger minimum and average walking velocity in response to the VRPs approaching from the middle and from the left as opposed to the right. While these findings contrast with an earlier observation from our own laboratory where no differences in average walking speed across directions of obstacle approach were observed 24, it should be noted that differences observed here were very small (< 0.1m/s). Nevertheless, it is possible that this difference is a product of a choice to give way to diagonally approaching interferers, which involve slower walking speeds. In our previous study, participants chose a front pass strategy in approximately 80% of the trials involving diagonal approaching interferers. In the present study, only 13.7% of the diagonal approaching interferers were circumvented with a front pass strategy. While we did observe differences, their magnitude is small and in alignment with prior observations which demonstrated that crossing pedestrians at obtuse angles (e.g., ahead of the pedestrian) requires mainly adjustments of trajectory as opposed to walking speed 10.
We investigated the obstacle circumvention strategies of healthy young participants in response to VRPs with and without facial masks and approaching from different directions. We observed that participants increased their anteroposterior clearance (i.e., onset distance) when VRPs wore a facial mask which allowed them to move away from the VRP’s walking path at a greater distance. This larger clearance could be a product of social factors related to a heightened awareness of an infection risk due to exposure to respiratory droplets, to an assumption that the approaching pedestrians prefer larger interpersonal distances or both. Lastly, participants reported feelings of anxiety towards community ambulation, and greater anxiety was associated with larger obstacle clearances, which suggests that those who feel more anxious towards community ambulation during the pandemic confinement period use this obstacle clearance strategy to reduce the risk of a COVID-19 infection. These results provide a better understanding of how the context surrounding the COVID-19 pandemic affects locomotor circumvention strategies, possibly due to an increase in anxiety related to community ambulation. Results further demonstrate the importance of considering social and psychological factors when examining complex locomotor behaviors, as well as the potential of VR for studying the influence of these factors on movement behavior in general.