The coffee you drink as a pick-me-up in the morning could also make you more open to persuasion, researchers say. Evidence from a new study suggests that this happens because caffeine revs up the brain, not because it generally boosts mood.

Previous studies have show that consuming caffeine can improve one’s attention and enhance cognitive performance, with 200 milligrams (equivalent to two cups of coffee) being the optimal dose.

Moderate doses of caffeine can also make you more easily convinced by arguments that go against your beliefs, say Pearl Martin of the University of Queensland in Brisbane, Australia, and her colleagues.

In 2005, her team published a paper suggesting that the compound primes people to agree with statements that go against their typical views because it improves their ability to understand the reasoning behind the statements.


Cooperative mood

But what if people were more likely to agree with others’ views simply because drinking coffee put them in a better mood?

To answer this question the team embarked on a new experiment involving nearly 150 volunteers. Subjects were asked about their attitude to controversial medical practices, such as voluntary euthanasia.

The participants were then given an orange-flavoured drink that either contained roughly 200 milligrams of caffeine or lacked the compound completely. Forty minutes later, when caffeine levels typically peak after consumption, subjects read arguments selected to contradict the particular opinion they held.

In order to determine whether caffeine made people more open to persuasion because it was promoting better mental function, or because it was improving mood, Martin’s team also threw distracting tasks into the mix. In one part of the experiment, researchers asked volunteers to cross out the letter o’ whenever it appeared in the text. In another part, they asked volunteers to wear headphones and discriminate between high and low-pitched notes by pressing a button as they read the arguments that contradicted their opinions.

Poor concentration

Volunteers who had consumed the caffeine drink were more likely to change their point of view than those who hadn’t. However, the more distracted subjects were, the less likely they were to have their views altered.

This, say the authors of the study, supports the idea that better mental function – rather than better mood – is the reason that coffee could make a person more easily persuaded, because the volunteers were only more open to persuasion when they could concentrate on and assimilate the persuasive argument.

In light of these findings, people who gulp down lattes at business meetings may want to reconsider how the drink is affecting them, the authors suggest.

Journal reference: European Journal of Social Psychology (DOI: 10.1002/ejsp.347)