Early bird really does get the worm, at least for older adults.

A study published in Psychology and Aging, has shown that there is truly noticeable differences in brain function throughout the day.

It showed that older adults perform better at cognitive tasks and activate the brain networks known to be responsible for paying attention and avoiding distraction.

"Time of day really does matter when testing older adults," said John Anderson, lead author of the study and a PhD candidate at the Rotman Research Institute at Baycrest Health Sciences and the University of Toronto.

"This age group is more focused and better able to ignore distraction in the morning than in the afternoon."

He said that the improved performance with cognitive tasks correlated with greater activation of the regions of the brain that control attention - the rostral prefrontal and superior parietal.   

In the study, the researchers compared 16 young adults ages 19 to 40 and 16 older adults ages 60 to 82. They preformed a series of memory tests throughout periods of the afternoon. During the test, there were random pictures and words presented as distractors. During the testing the participants' brains were imaged using fMRI to see what areas of the brain were being activated.

They found that older adults were 10 percent more likely to be distracted by the extraneous information than younger adults.

The fMRI data confirmed that older adults had less activation of the attentional areas. In fact, some of the older adults were idling with their brains in default.

Then the researchers tested 18 older adults in the morning. Researchers noticed that the adults did much better. They were less distracted than the other group. They activated similar areas of the brain as the younger adults.

"Our research is consistent with previous science reports showing that at a time of day that matches circadian arousal patterns, older adults are able to resist distraction," said Lynn Hasher, senior author of the study.

This study comes with a warning for researchers who want to measure cognitive function in older adults. Ignoring the time of day that the adults are being tested could create an inaccurate picture of cognitive function.