Scientists have discovered why men are so keen to ask their date in for a coffee after a night out – it seems caffeine makes us more likely to say "yes".

Moderate amounts of the coffee stimulant can increase people’s willingness to be persuaded, say researchers.

Scientists found that after consuming caffeine, volunteers were more likely to agree with persuasive arguments.

Two experiments were conducted involving about 140 students who were questioned about how they viewed voluntary euthanasia and abortion.

Volunteers were then asked to read persuasive messages about the subject that were opposed to their own opinions.

Before reading the arguments, they were asked to drink either straight orange juice or juice laced with the caffeine equivalent of two cups of coffee.

Finally, they were tested again on their attitude to the controversial topics.

Under non-distracting conditions, caffeine increased the chances of the students changing their points of view.

Dr Pearl Martin, from the school of psychology at the University of Queensland, Australia, who led the research, said: "Given the numerous situations in which people are exposed to persuasive arguments, these results could have many applied implications.

"Consider how caffeine-containing products, such as coffee, tea, cola or energy drinks, might affect how persuaded a person is when, for example, listening to advertisements or a political speech on the radio or TV, reading a film review or in a business meeting to discuss work-related issues."