>> Studying the Effects of Aging on Cognition

The dramatic increase in birth rate that followed World War II stimulated research into infancy and early education. The babies from the "baby boom" have now aged; according to the National Institute of Aging, by the year 2025, one out of every five North Americans will be at least sixty-five years old. The "graying" of America has led researchers to study cognition across the human life span.

Despite widespread stereotypes to the contrary, intellectual decline is not an inevitable part of aging. However, it is clear that aging does affect both memory and the speed of processing, and that these changes can have implications. The National Highway and Traffic Safety Institute (NHTSA) reports that even though elderly drivers tend to be careful and law-abiding, their relative risk of being involved in a vehicular accident is significantly higher than that of younger drivers.

Sensory-perceptual changes that occur with age may account for some of the increased risk. Elderly drivers are more likely than younger drivers to have visual impairments that are a result of cataracts (clouding of the lens). After age sixty, changes in the three major structures of the eye become common. The cornea is more likely to become clouded, the lens is less flexible, making it harder to focus properly; and the retina tends to degrade. With each successive decade, these changes become more apparent in most people. Thus, the view through the windshield may not be as sharp as it once was.

  
Photo: Dr. Chip Scialfa, Psychology Department,
University of Calgary.

However, changes in visual acuity among the elderly don't tell the whole story. David Shinar and Masha Maltz, two psychologists with interests in human factors and traffic safety, tested older and younger individuals as they viewed typical driving scenes. All of their participants had their vision tested to exclude individuals with visual difficulties. Using a sophisticated piece of equipment that tracks where the eye is looking, Shinar and Maltz were able to record the gaze points of younger and older drivers as they scanned driving scenes. In one portion of their study, they gave their participants a scene similar to the scene you are about to see. Participants were first asked to find the number 1, then 2, then 3, and so on until the viewer had found all the numbers present in the image. The quicker a person can search and identify the features, the quicker he or she would perform the task.

Photo: Dr. Chip Scialfa, Psychology Department,
University of Calgary.

Shinar and Maltz found that older drivers took significantly longer than younger drivers to find the numbered items. Their results are presented in the graph below.

In another part of their study, Shinar and Maltz presented a series of pictures taken from the perspective of a driver and asked their older and younger subjects to look at each scene as if they were driving a car. The pictures contained features that would be important to any driver: a rearview mirror, pedestrians, and other automobiles turning into the path of the "driver." Shinar and Maltz found that older drivers took significantly longer to identify and extract important information from each scene than did the younger drivers. This research suggests that older drivers on the average take longer than younger drivers to decide which visual features in a scene represent critical information.
At this point you might conclude that elderly drivers represent a danger to themselves and others, but in fact many older drivers are quite safe. Researchers interested in aging and traffic safety are currently investigating the following questions:

• Can we quickly and fairly differentiate dangerous from safe elderly drivers?
• Are some situations especially hazardous for older drivers?
• Do some medications common among the elderly present additional risk?
• Can training programs tailored for the aged be help them maintain their license?

Discussion Questions:

Web Links:

NTSA, Older Drivers: www.nhtsa.dot.gov/nhtsa/whatis/regions/Region02/02older.html.
NTSA, Driving Safely While Aging Gracefully: www.nhtsa.dot.gov/people/injury/olddrive/Driving%20Safely%20Aging%20Web/index.html.

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