Researchers found that it is not that younger people are able to remember more than older people but their memories seem better because they retrieve them in higher definition.
Philip Ko of Vanderbilt University in the US, led the research team which focused on visual working memory, a person's ability to briefly retain a limited amount of visual information in the absence of visual stimuli.
The team's examination of why this function is reduced during the course of healthy ageing took the multiple stages of encoding, maintenance, and the retrieval of memorised information into account.
They ran 11 older adults of around 67 years of age and 13 younger adults of approximately 23 years of age through a task called 'visual change detection'.
This task consisted of viewing two, three or four coloured dots and memorising their appearance. These dots disappeared, and then after a few seconds the participants were presented with a single dot appearing in one of the memorised colours or a new colour.
The accuracy of their response ('same' or 'different') was considered to reflect how well they memorised the colours. This accuracy of response is referred to as 'behavioural measure'.
Electroencephalographic data was also collected from the participants as they performed the task for a neural measure of their memory capacity.
Ko found that while behavioural measures indicated a lower capacity in older adults than younger adults to memorise items, the neural measure of memory capacity was very similar in both groups.
In other words, during the maintenance stage, both groups stored the same number of items.
The researchers suggest that older adults store the items at a lower resolution than younger adults, resulting in impaired recollection.
Unlike older adults, younger adults may be able to use perceptual implicit memory, a different kind of visual memory, to give them a 'boost' when they are trying to retrieve the stored information.
"We don't know why older adults perform poorly when their neural activity suggests their memory capacity is intact, but we have two leads," Ko said.
"First, further analysis of this current dataset and other studies from our laboratory suggest that older adults retrieve memories differently than younger adults.
"Second, there is emerging evidence from other labs suggesting that the quality of older adults' memories is poorer than younger adults.
"In other words, while older adults might store the same number of items, their memory of each item is 'fuzzier' than that of younger adults," Ko said.
The study appears in the journal Attention, Perception & Psychophysics, published by Springer.