As we age, we struggle to use landmark-based navigation

Deficits in how we process visual info cause a reliance on geometric features.

Diana Gitig – Sep 30, 2019 10:31 am | 62

People exploring the Maze at Glendurgan Garden, Cornwall, England, UK. (Photo by: Geography Photos/Universal Images Group via Getty Images) Credit: Geography Photos | Getty Images

We don’t know how older people navigate around their environments, only that they don’t do it as well as they once did. It has been posited that they favor egocentric strategies, focusing on the relationship between themselves and the objects around them. That could reduce their perspective on the environment compared to allocentric strategies, which focus on the relationships among the objects, regardless of viewpoint.

Either way, they need to use the objects around them as visual cues. A new study suggests that their declining navigation skills aren’t the result of a change in strategy but that they occur even before they get to that, in how they process visual cues.

People generally harness two types of visual cues for navigation. Geometric cues include things like the brick walls of a building or a hedge border; landmarks like that really gnarled dead tree trunk or that broken street lamp. Children like geometric cues, and young adults favor landmarks.

Virtual reality studies of older adults have yielded conflicting results as to which type they tend to rely on more. But other studies have indicated that virtual reality isn’t such a great way to assess the capabilities of older adults. So a group of scientists tried to figure out how older adults navigate the way that researchers have traditionally tried to figure out how animals navigate: they ran them through a maze.

Twenty younger (ages 19 to 37) and nineteen older (ages 61 to 81) adults were oriented in an indoor, street-like grid. They were then spun around with their eyes closed, just as if they were about to pin the tail on a donkey or swing at a piñata. But no fun and games for them; instead they were led to a random point in the enclosure.

After opening their eyes and getting their bearings, they had to find a goal: a marked square on the floor. After eight rounds, the researchers sneakily rotated all of the walls, so now geographic and landmark cues were in conflict regarding the location of the goal. If you remembered the goal as being in the corner between the short and long walls, you were set. But if you remembered it as being between the brown door and the green window, you were now screwed.

As expected from previous work, most younger adults navigated via landmarks. But most of the older adults preferred the geometry of the environment. So they headed right to the goal zone (well, three-quarters of them did; a quarter went to the rotationally opposite corner, which had the same geometry). Their reliance on the landmarks led the younger adults astray. There were no gender differences detected.

Older people took longer to learn their way around the maze and took more roundabout routes to find the goal, though. Their increased learning time was because they looked at the same cues around them multiple times, not because they looked around more slowly.

Based on analysis of the participants’ eye and body movements as they walked through the maze, the researchers concluded that neither one accounted for their preference for geometric cues over landmarks. Their memories were fine, so it wasn’t that they couldn’t remember features. Rather, this preference was due to a cognitive impairment in both egocentric and allocentric strategies: it was difficult for the older people to infer their position, or that of the goal zone, from the perspective of any particular landmark.

Navigating requires the coordination of the neural processes mediating multi-sensory integration, contextual learning, and spatial cognition, so isolating which aspect fails as we age has been difficult. This study indicates that the problem lies, not in navigational strategy, but in cue-processing. Regardless, those older adults found an effective way to reach their goal when the maze was flipped.

Nature Human Behaviour, 2019. DOI: 10.1038/s41562-019-0718-z (About DOIs).