Vision keeps us out of trouble, especially when we, or another object, is in motion.
It can let us know when to slam on the brakes in our car, or when someone at the grocery store is about to hit us with a shopping cart. Our body uses something called optic flow to gather visual information about the environment around us. Optic flow looks a little bit like the Millennium Falcon in hyper drive (warp drive for you Star Trek people): as we move towards a point, objects around us change in visual size and location. As we move, we use visual information from optic flow to spatially update our position in our environment. Spatial updating gives us an understanding of our situation in the surrounding environment.
As we age, we find that our eyes “aren’t what they used to be;” our ability to process information from optic flow degrades. This can cause serious problems. In Sekuler and Blake’s book, Perception, they talk about research in the spatial processing of older participants. They draw the conclusion that “diminished ability to judge direction of heading could contribute to age-related errors of locomotion and result in an increased incidence of falling accidents.” They mention that this is due to an inability to process information from optic flow. If your brain is unable to tell your body the direction you are heading, you can imagine what a danger zone the world could be!
Compounding this problem of visual aging, are conditions, like Alzhiemer’s, that cause people to lose the ability to identify familiar settings, like their own house. This gradual degradation of environmental familiarity could cause even the most visited location, such as the bathroom, to become a new and challenging path.
However, there is a difference in the types of spatial updating we can use to understand our environment.
Online spatial updating
Part of spatial updating is considered to be an “online” process, where the spatial relationship to our immediate environment is continually adjusted through tiny moment-to-moment calculations. This helps us walk, run, move, and maneuver in a space.
Offline spatial updating
Spatial updating can also leverage our long-term memory so that it can assist “offline.” For example: learning the layout of a room, memorizing a map, etc. We would not actually need to walk the full room to understand its layout; we could just look at the map and remember any dimensions or obstacles, like a desk. However, we would still need online spatial updating to tell us our location relative to the desk so that we did not collide with it. Current research on the theory of offline spatial is inconclusive on when and how often this information is accessed.
Because both online and offline spatial updating require use of memory, Alzhimer’s patients experience extreme difficulty understanding their surroundings. Not only would they no longer remember obstacles like a loose floor board, or a flight of stairs, but they would encounter addition trouble acting navigating those items in real time. This is great information for architects, engineers, interior designers, nurses, caregivers, and anyone else that has the task of designing for or caring for the elderly.
Hodgson, Eric. & Waller, David. (2006) Lack of Set Size Effects in Spatial Updating: Evidence for Offline Updating. J Exp Psychol Learn Mem Cogn. Volume 32(4). Pages 854-66.