Over-65s cannot cope with visual distractions when driving

Older adults were found to have a processing speed three times slower than some of the younger people surveyed. Photo / iStock

Older people have vision that is three times slower than younger people when coping with distractions, which could make them less safe drivers, a study has found.

Research led by psychologists at Nottingham Trent University found that over-65s processed visual information just as quickly as 18 to 30-year-olds when asked to recreate a single object's orientation after it had briefly appeared on a computer screen.

But when additional "distracting objects" were added to the screen, older people became significantly slower at processing the original object.

Writing in the Journal of Vision, the researchers say they demonstrate evidence of age-related decline in the speed at which visual information is processed. They believe the study carries important implications for everyday situations such as driving.

"The difference in task demands of having to remember two items rather than one seems small, yet this led to a large slowing in processing speed for older people," said Dr Duncan Guest, a psychologist in Nottingham Trent University's School of Social Sciences.

"The work clearly has implications for everyday situations in which visual scenes are composed of multiple objects - our research suggests older people would be significantly slowed in such situations. Drivers, for instance, need to search cluttered visual scenes for targets such as road signs and buildings, while encoding and storing information about multiple other vehicles or hazards."

Legally, there is no age at which people must stop driving. The onus is on the driver to decide when he or she can no longer cope. From the age of 70 all drivers must renew their licence every three years, but there is no practical test and no medical, just a form asking drivers to declare they are still safe, and to disclose medical conditions that could impair driving, such as loss of vision. A GP and optician can declare a driver unfit if they believe the person represents a danger.

According to the Association of British Insurers, people over 70 are half as likely to be involved in accidents as 18 to 20-year-olds. This is partly because older people will often choose not to drive at night or in bad weather and often make short, familiar journeys. However, previous studies have shown that it takes older people eight times as long for their eyes to recover from a bright light than for a 16-year-old.

In the first experiment, participants were asked to remember where an object had been on screen after it vanished. In a second, four extra objects appeared as a distraction, while in the third task, two objects were simultaneously presented; the volunteers were told which was the target object only after it had disappeared. They then had to say which has been the target.

These tasks examined how encoding and retaining information from multiple stimuli affected processing speed.

While there was no significant difference in experiment one, older adults were found to have a processing speed three times slower than younger

people in experiments two and three.

"Previous work has shown that older people sometimes take longer than younger adults at tasks requiring visual processing - but until now it had been less clear at what point this slowing occurred and, in particular, whether there was slowing in the rate of processing visual information," Dr Guest said.