Older people are less likely to recognise they have made a mistake, a new study has found.

Younger people were more willing to put up their hand and admit they had erred but older people more adamant they did not made a mistake in tests.

And it is because as we age we are less likely to recognise when we have made a mistake.

And the findings offers new insight into how older people perceive their decisions, and especially how they view their performance, such as whether they are fit to drive or how often they have take their medicine.

Researchers at the University of Iowa devised a simple, computerised test involving looking away from an object appearing on the screen to gauge how old and young people did not look away and whether they admit it.

Assistant Professor Jan Wessel, in the Department of Psychological and Brain Sciences said: "The good news is older adults perform the tasks we assigned them just as well as younger adults, albeit more slowly.

"But we find there is this impaired ability in older adults to recognise an error when they've made one.

"Realising fewer errors can have more severe consequences because you can't remedy an error that you don't realise you've committed."

The study published in the journal Neurobiology of Aging involved 38 volunteers with an average age of 22 and 39 with an average age of 68.

The tests involved looking away from a circle appearing in a box on one side of a computer screen.

While the test was simple, younger adults couldn't resist glancing at the circle before shifting their gaze about 20 per cent of the time on average.

Prof Wessel explained that was expected as it's human nature to focus on something new or unexpected, and the researchers wanted the participants to err.

After each failed instance, the participants were asked whether they had made an error.

They then were asked "how sure" and used a sliding scale from "unsure" to "very sure" to determine how confident they were about whether they had made a mistake in the test.

The younger participants were correct in acknowledging when they had erred three quarters of the time.

Yet the older test-takers were correct in just two thirds - 63 per cent - of the time when asked whether they had erred.

That means in more than one-third of instances, the older participants didn't realise they had made a mistake.

Even more, the younger participants who made an error on the test were far less certain than the older participants that they were correct.

In other words, the younger adults hedged more.

Prof Wessel said: "It shows when the younger adults thought they were correct, but in fact had made an error, they still had some inkling that they might have erred.

"The older adults often have no idea at all that they were wrong."

How much the participants' pupils dilated as they took the tests were alos measured.

In humans and most animals, pupils dilate when something unexpected occurs, triggered by surprise, fright, and other core emotions.

It also happens when people think they've blundered.

The younger adults' pupils dilated when they thought they erred and this effect was reduced when they committed errors they did not recognise.

In comparison, older adults showed a strong reduction of this pupil dilation after errors that they recognised and showed no dilation at all when they committed an error they did not recognise.

Prof Wessel said: "That mirrors what we see in the behavioural observations that more often they don't know when they've made an error."