Testosterone makes men less likely to question their
impulses: men given doses of testosterone performed
more poorly on a test designed to measure cognitive
reflection than a group given a placebo.
A study conducted by researchers from Caltech, the
Wharton School, Western University, and ZRT
Laboratory tested the hypothesis that higher levels
of testosterone increase the tendency in men to rely
on their intuitive judgments and reduce cognitive
reflection, a decision-making process by which a
person stops to consider whether their gut reaction
to something makes sense.
"What we found was the testosterone group was
quicker to make snap judgments on brain teasers
where your initial guess is usually wrong," says
Caltech's Colin Camerer, the Robert Kirby Professor
of Behavioral Economics and T&C Chen Center for
Social and Decision Neuroscience Leadership Chair.
"The testosterone is either inhibiting the process
of mentally checking your work or increasing the
intuitive feeling that 'I'm definitely right.'"
The study, which is one of the largest of its type
ever conducted, included 243 males who were randomly
selected to receive a dose of testosterone gel or
placebo gel before taking a cognitive reflection
A math task was also given to control for
participant engagement, motivation level, and basic
The questions included on the cognitive reflection
test are exemplified by the following:
A bat and a ball cost $1.10 in total. The bat costs
$1 more than the ball.
How much does the ball cost?
For many people, the first answer that comes to mind
is that the ball costs 10 cents, but that's
incorrect because then the bat costs only 90 cents
more than the ball.
The correct answer is that the ball costs 5 cents
and the bat costs $1.05.
An individual prone to relying on their gut
instincts would be more likely to accept their first
answer of 10 cents.
However, another person might realize their initial
error through cognitive reflection and come up with
the correct answer.
Participants were not limited on time while taking
the test and were offered $1 for each correct answer
and an additional $2 if they answered all the
The results show that the group that received
testosterone scored significantly lower than the
group that received the placebo, on average
answering 20 percent fewer questions correctly.
The testosterone group also "gave incorrect answers
more quickly, and correct answers more slowly than
the placebo group," the authors write.
The same effect was not seen in the results of the
basic math tests administered to both groups. The
results "demonstrate a clear and robust causal
effect of [testosterone] on human cognition and
decision-making," they conclude.
The researchers believe that the phenomenon they've
observed can be linked to testosterone's effect of
increasing confidence in humans.
Testosterone is thought to generally enhance the
male drive for social status, and recent studies
have shown that confidence enhances status.
"We think it works through confidence enhancement.
If you're more confident, you'll feel like you're
right and will not have enough self-doubt to correct
mistakes," Camerer says.
Camerer says the results of the study raise
questions about potential negative effects of the
growing testosterone-replacement therapy industry,
which is primarily aimed at reversing the decline in
sex drive many middle-aged men experience.
"If men want more testosterone to increase sex
drive, are there other effects? Do these men become
too mentally bold and thinking they know things they
For more information
Single dose testosterone administration impairs
cognitive reflection in men.