Where do we look when we walk?

May 08, 2021
An example of a hiking trail in British Columbia where one must decide where to look and step.

New SFU study sheds light on how we decide where we look and step when walking in cluttered environments.

Trying to walk while blindfolded easily demonstrates the importance of visual cues needed to manage precise foot placement and avoid falling. But how do we make these decisions when there is an abundance of visual cues to choose from? New research from SFU’s Sensorimotor Neuroscience Lab shows that people weigh a variety of factors before deciding where to step.

The study, published in Current Biology as part of Javier Domínguez-Zamora’s doctoral research under the supervision of professor Dan Marigold in the Department of Biomedical Physiology and Kinesiology, provides insight into how people direct gaze to acquire relevant information to inform their decision where to place their feet when walking, stepping to avoid obstacles, negotiating stairs or curbs, and when walking across unstable or irregular terrain.

Marigold explains the decisions that we make when walking. “Consider the example of hiking, where there are several choices of step locations. Now consider that the terrain located directly in front of you is uncertain. Maybe you’re not sure how soft the mud is, or whether the shine on the rock means it is slippery. Do you step wide, which requires you to expend more energy, or do you take your chances with the uncertain terrain in front?”

In Domínguez-Zamora’s and Marigold’s experiment, participants were tasked with deciding which of two targets to step on as they walked across a path in the lab. Their goal was to step precisely onto the centre of the target. The target varied in its blurriness, creating uncertainty as to the location of its centre. The other target choice required a wider, more effortful step, but it was easier to locate the centre of it to ensure foot-placement accuracy.

Using a mobile eye tracker that records a person’s gaze location, the team found that how a person explored the targets with their eyes dictated where they stepped.  

Roughly half of the participants looked at both targets to gain information. These people were more likely to choose to step on the more certain but more effortful target location.

In contrast, the other half of participants only looked at and stepped on the less effortful but blurry target.

The researchers suggest that acquiring information about the environment, being certain of one’s actions, and the effort to move one’s body are factors that interact to dictate how we direct our eyes and the decision of where to move. They found overwhelming evidence that  people weigh these factors differently.

“Every person is different, and the variety of decisions that we make during our life reflects those differences. Studying the motives that determine why we decide to move in the way we do might help us understand the behavioural changes that occur during development, aging, and with neurological disorders that affect movement,” says Domínguez-Zamora.

“Where and when a person looks relative to where and when they step is critical for ensuring safe mobility, but this gaze-stepping relationship is altered in people with different neurological impairments and eye diseases, such as glaucoma,” says Marigold. “If we can better understand how people make decisions about where to direct their eyes and the paths they choose to take, then in the future, we might be able to design more effective gaze-training interventions to improve mobility—and reduce the likelihood of falls—in various populations.”