Brains remain sharp until 60, study suggests

Brains remain sharp well into middle age, contrary to popular assumptions that mental speed declines from our 20s and 30s, research suggests.

A study of 1.2 million people, aged 10 to 80, found mental speed remained relatively stable between 30 and 60 - but caution tended to grow with age.

Researchers at Heidelberg University in Germany used an online task to estimate people's decision-making times.

They published their findings in Nature Human Behaviour.

The scientists showed participants a series of online images and asked them to place them in two categories - good or bad - pressing different buttons to do so.

They suggest the task involves distinct processes, including mental speed - roughly defined as the rate at which we process information to make a decision - decision caution, which looks at the time taken to consider information before making up our minds, and then the time involved in actually pressing a button.

Using mathematical models, researchers were able to estimate the speed at which participants completed each part of the process.

They found that while the average time to complete the overall task got worse after the age of 20, the mental speed of processing information did not start to slow until 60.

The study found:

• people under 18 were least cautious and most willing to forgo accuracy for speed.

• caution around decisions increased between ages 18 and 65

• people also took longer to press the relevant button as they got older

Scientists accept there are likely to be many different processes involved in making decisions and say it is possible that other factors, such as previously formed opinions, also affect decision-making speed.

They conclude: "For large parts of the human lifespan and typical work careers, our results challenge the widespread notion of an age-related slowdown in mental speed."