London, May 5 (IANS): As we get older we tend to hold less information in our minds. But that has less to do with cognitive decline and more with distractions, says a new study.

While 16- to 17-year-olds can hold an average of 6.5 numbers in mind for a short time in their "working memory", this drops to five numbers for 75- to 79-year-olds.

Being able to effectively ignore distraction seems to be crucial for working memory, said the large-scale study conducted using a smartphone game as part of the Great Brain Experiment.

In younger adults, it has been shown that those who can hold a lot of information in their minds not ony have a good working memory but are also good at ignoring distraction.

Those with poor working memory seem to unnecessarily remember distractions.

It has been argued that our ability to focus on what's important, while blocking out irrelevant information, may go some way towards explaining how much we can hold in our minds.

"Our ability to ignore distraction also declines with age, and it may be this that underlies the age-related decline in working memory capacity," the researchers from University of Birmingham said.

In the experiment, 29,000 people between the ages of 18 and 69 played a smartphone game in which they had to remember the positions of red circles.

"As the game progressed, more and more circles were shown, until the player couldn't remember them and started making mistakes. This told us how many items they could hold in mind -- their 'working memory' capacity," they said.

While playing the game, yellow circles also appeared, which the players had to ignore.

According to researchers, there are two different types of distractions. The first type occurs when we are putting information into our memories.

With the second type, the information is in our memory, and we are trying to hold on to it.

Older people showed the most decline in their ability to ignore distractions introduced after they had memorised information.

"These results indicate that when older adults hold information in mind, that information is particularly vulnerable to distraction. These findings could lead to new ways to improve working memory in older adults," they added.