Simply telling people that an energy drink has been added to their alcoholic beverage can make them feel more intoxicated, daring and self-confident, scientists say.
Researchers, including those from University of British Columbia in Canada, conducted a trial of 154 young men. The participants were told they would drink a cocktail of an energy drink, vodka and fruit juice.
Though all drinks had the same ingredients, they had different labels - Red Bull and vodka, a vodka cocktail or a fruit juice cocktail.
The effect of the label alone on participants' self- assessment of intoxication was remarkable, researchers said.
They found that participants who believed they were drinking an energy drink and alcohol cocktail were more likely to believe themselves quite drunk and uninhibited.
This was especially true among those who had a strong belief that mixing energy drinks with liquor would boost the effects of liquor, researchers said.
Researchers found labelling the same cocktail as vodka and Red Bull increased perceived intoxication by 51 per cent, compared to labelling it a vodka cocktail or a fruit juice cocktail.
It also increased the young men's intentions to approach and "chat up" women, and their confidence that they would welcome it, researchers said.
It also led to more risk-taking in a gambling game. All these effects were stronger for the participants who most strongly believed that energy drinks boost the effects of alcohol and that being intoxicated reduces inhibitions and increases risk-taking.
"Beliefs that people have about a product can be just as important as the ingredients of the product itself," said Pierre Chandon from Sorbonne University in France.
The study appears in the Journal of Consumer Psychology.