A Kansas University professor has revealed in his study that the slow processing speed of an aging brain is the prime reason for healthy older adults experiencing communication problems.
Professor Susan Kemper devised a dual-task procedure that precisely measured and analyzed the ability of young and older adults to do two things at once - keep a cursor on a moving target on a computer screen while responding to questions, and secondly to measure how aging affects communication abilities.
The dual-task procedure allowed the researchers to track the moment-by-moment fluctuations in individuals' tracking performances as a function of what they were saying.
While it was not surprising that younger adults did better at dual-tasking, both young and older adults hit a "functional ceiling" when the target was moving rapidly or when the questions required thoughtful and complex responses.
But another pattern also emerged: Young adults often limited what they were saying to stay with the rapidly moving target, while older adults sacrificed target tracking to provide complex and thoughtful responses.
"We didn't find much evidence that working memory or long-term memory play a role in dual-tasking, but we think that processing speed does," said Kemper.
"What I think is going on is that you have to rapidly switch your attention from tracking to talking, going back and forth pretty rapidly, and that's where the processing speed really comes in. Older adults seem to be slower at switching between tasks so their functional ceiling is lower," he said.
Older adults also needed recovery time after producing a complex sentence.
The study appears in the Journal of Gerontology: Psychological Sciences.