11 March 2011

Older drivers 'see too much'

In October 2009 we reported on research by Adam Gazzaley of the University of California in an item entitled “Does your brain slow down as you get older?” The researchers, who were looking into the speed at which older people perform mental tasks relative to their younger counterparts, found that the brains of older people were not slower but that they appear slower because older people’s brains are not as good at blocking irrelevant information. They therefore are more easily distracted and find it harder to concentrate on the task in hand.

I mention this as recent research by Professor Duje Tadin at the University of Rochester in New York has produced similar conclusions.

His research was investigating a worrying phenomenon of ageing that results in older drivers failing to notice other cars, pedestrians and cyclists moving around them. For some time this has been blamed on a reduced ability to notice moving objects, but the research suggests that it is actually caused by an inability to separate the objects from the background.

In healthy young brain a region called the middle temporal visual area actively suppresses irrelevant background motion so that the person can concentrate on the more important movements of smaller objects in the foreground. Previous studies have found that elderly people, as well as those with psychological conditions such as schizophrenia and depression are better at perceiving motion in the background.

The problem is that since our brains are only capable of consciously processing a limited amount of information at any one time, this heightened awareness of the background serves as a distraction that draws our attention away from the more important foreground objects.

"The amount of visual information around us is huge, and we don't have the brain power to process it all," Tadin said. "Evolutionarily speaking, moving objects are the most important visual features to detect quickly, because they could be your lunch or they could want to eat you for lunch. It just makes sense that our vision prioritizes processing them."

The results of both studies would therefore suggest that a natural part of the ageing process is an improvement in our ability to perceive things holistically, but decrease in our ability to concentrate on the specifics of any one thing.

While the implications of this research for the medical professions lie in improved diagnosis of certain medical conditions, the implication for employers is that to get the best from their staff they should consider these age-related differences when assigning tasks.

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