If you struggle to remember names and numbers or frequently fail to follow the plot of a film, help could be at hand.

Scientists say the problem is that you know too much – and you need to declutter, or spring-clean your mind.

Experiments show that the memory lapses that come with age are not simply due to brain slowing down.

Instead, they can be blamed on the well-used brain finding it more and more difficult to stop irrelevant information interfering with the task in hand.

The first step in the study was to compare the working memory of the young and old. Working memory involves holding information in mind while manipulating it mentally.

In the context of the study, it involved giving the volunteers groups of sentences and asking them to work out whether each line made sense – and to remember the last word of each sentence.

Overall, the younger people, who had an average age of 23, did better, the Quarterly Journal of Experimental Psychology reports.

The Canadian researchers then did a second experiment to see what was hindering the older volunteers, who had an average age of 67.

This involved being shown a picture of eight animals and being asked to memorise the order in which the creatures appeared.

The volunteers were then shown dozens of the pictures and asked to click on their computer mouse when the first animal in their memorised sequence occurred, then the second and so on.

The older adults found it more difficult to progress, suggesting the previous picture was stuck in their mind.

Mervin Blair, of Montreal’s Concordia University, said: ‘We found that the older adults had more difficulty in getting rid of previous information.’

Previous research has found that the part of the brain that keeps embarrassing thoughts in check also weakens with age, leading to people losing some of their inhibitions.

In other words, outspoken old people aren't being rude - they just can't hold their tongues.