People on the go follow the flow

It’s easy to walk from the living room to the hallway, the hallway to the bathroom, and so on. Yet scientists have long argued about how people navigate to a destination.

A virtual reality device that allows individuals to walk through a world in which the laws of optics systematically go awry may help settle this debate, a team of cognitive scientists reports in the February Nature Neuroscience.

It’s possible that a person moving toward a target aligns it within the tunnel-like rush of visual stimuli, known as optic flow, that bombards the eyes. In contrast, observers may gauge the direction of a target relative to their own body by centering the target in their line of sight and then moving forward.

Or the visual system employs both of these tactics, depending on how much optic flow is provided by one’s surroundings, contend William H. Warren of Brown University in Providence, R.I., and his coworkers in their report.

In their study, 10 volunteers wore head-mounted devices that enabled them to walk through virtual environments in which optic flow was distorted so that the person veered slightly to one side. In sparse settings that produced little optic flow, volunteers ended up walking a curved path to their destination. Each observer used the minimal flow information to walk forward a few feet. He or she then stopped, turned toward the virtually displaced destination, and again moved forward. Each person repeated this process several times.

In environments with features such as textured floors that provided lots of optic flow, volunteers walked straighter, more accurate paths toward targets. They continuously monitored optic flow and used feedback from it to readjust their heading, often adopting a slightly sideways gait, the researchers say.