The best way to increase your chances of success in a job interview, exam, or driving test is to take it in the morning, scientists have found.
Danish researchers found that "cognitive function" - or the ability to perform tests involving simple brain power - diminished throughout the day.
They studied two million tests taken by children aged eight to 15 over three years, and found that their results dropped by just under a per centage point for each hour later that the test was taken.
This meant scores for a test taken at 9am were likely to be 5.4 per cent higher than if the same exam was taken at 3pm.
Scientists from the Danish National Centre for Social Research concluded that this "cognitive fatigue" could apply in any situation that requires brain power.
However, the researchers found that the situation could be avoided not by taking exams earlier in the day, but by having proper breaks.
They discovered that taking a 20 to 30 minute break before a test improved results by an average of 1.7 per cent.
The scientists took into account factors that could skew results, such as gender, income, and the day of the week.
The report, in academic journal PNAS, said: "As the day wears on students become increasingly fatigued and consequently more likely to underperform on a standardised test."
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