"It's known that older adults are more easily distracted. We think we've found a mechanism in the brain to explain this," Grady said. "The functional changes are detectable by middle age."
The study, funded by the Canadian Institutes of Health Research, is published in the Journal of Cognitive Neuroscience.
As a practical matter, many researchers are trying to learn whether multi-tasking techniques meant to improve communication and productivity could instead make people scatterbrained, leaving them lethargic and forgetful.
By one published estimate, the typical office worker is interrupted every three minutes.
Scientists from King's College at the University of London, for example, recently determined that people trying to juggle phone calls, e-mail and other routine office distractions suffered a greater loss of IQ than someone smoking marijuana.
