Consume Caffeine, Change Your Mind?
Caffeine May Leave People More Open to Persuasion, Study Shows
June 5, 2006 -- Planning to ask your boss for a raise? You might want to do
it over a cup of coffee.
A new study reports people may be more easily persuaded to change their
opinion after consuming caffeine.
Researchers in Brisbane, Australia found undistracted university students
were more persuaded by arguments made after they drank a caffeine-laced
Caffeine has been shown to boost attention. But few studies have checked
caffeine's effects on persuasiveness, note Pearl Martin, PhD, and colleagues.
Martin works at the University of Queensland's School of Psychology.
Caffeine is found in coffee, tea, some soft drinks, and other products. It's
often consumed in settings that could involve "persuasive
communication," note Martin and colleagues.
For instance, people might drink coffee while reading the newspaper or
"The practical implications of our findings to 'real world' settings are
many and therefore warrant future investigation," the researchers write in
the European Journal of Social Psychology.
Martin's study included 120 university students, half of whom were
First, the students took surveys about their views on a controversial topic.
For men, the topic was abortion. For women, it was euthanasia, defined in the
study as a person's right to end his life if he has a terminal illness.
Later, researchers served orange juice to the students. Some got plain
orange juice, which has no caffeine. The others got juice with caffeine
The students didn't know which they received. They had previously been asked
not to consume caffeine or alcohol, beginning the night before the
None of the students was pregnant, a smoker, or a heavy user of
Making the Case
The researchers told the students to drink the orange juice quickly. The
experiment began 40 minutes after they had finished the drink in order to allow
the caffeine to take its full effect.
Next, researchers gave the students publications to read which made points
counter to their opinions on abortion or euthanasia. Men received the abortion
publication; women the one about euthanasia.
Some students were told to pay close attention to the points made in the
publication. Others were given a distracting task, such as crossing out the
letter "o" throughout the text.
Afterwards, all students rated how much -- if at all -- their opinions had
changed. The point was to see if caffeine and distractions affected
Open to Persuasion
Students who drank the caffeine-laced juice were more apt to be persuaded by
the publications, the study shows.
But there was a catch. Those who had done the distracting task stuck with
their original opinion, even if they'd had the caffeinated orange juice.
Caffeine may have made students more likely to change their minds, but only
if they weren't distracted.
It's not clear why caffeine increased persuasiveness. Maybe caffeine
affected how the students processed the message. Or perhaps caffeine upped
emotional arousal and/or improved mood, making the students more likely to
agree with the message, the researchers note.