Don't make
major decisions on an empty stomach
University of Dundee
We all know that food shopping when
hungry is a bad idea but new research from the University of Dundee suggests
that people might want to avoid making any important decisions about the future
on an empty stomach.
The study, carried out by Dr
Benjamin Vincent from the University's Psychology department, found that hunger
significantly altered people's decision-making, making them impatient and more
likely to settle for a small reward that arrives sooner than a larger one
promised at a later date.
Participants in an experiment
designed by Dr Vincent were asked questions relating to food, money and other
rewards when satiated and again when they had skipped a meal.
While it was perhaps unsurprising
that hungry people were more likely to settle for smaller food incentives that
arrived sooner, the researchers found that being hungry actually changes
preferences for rewards entirely unrelated to food.
This indicates that a reluctance to defer gratification may carry over into other kinds of decisions, such as financial and interpersonal ones. Dr Vincent believes it is important that people know that hunger might affect their preferences in ways they don't necessarily predict.
There is also a danger that people
experiencing hunger due to poverty may make decisions that entrench their
situation.
"We found there was a large
effect, people's preferences shifted dramatically from the long to short term
when hungry," he said. "This is an aspect of human behaviour which
could potentially be exploited by marketers so people need to know their
preferences may change when hungry.
"People generally know that
when they are hungry they shouldn't really go food shopping because they are
more likely to make choices that are either unhealthy or indulgent. Our
research suggests this could have an impact on other kinds of decisions as
well. Say you were going to speak with a pensions or mortgage advisor -- doing
so while hungry might make you care a bit more about immediate gratification at
the expense of a potentially more rosy future.
"This work fits into a larger
effort in psychology and behavioural economics to map the factors that
influence our decision making. This potentially empowers people as they may
forsee and mitigate the effects of hunger, for example, that might bias their
decision making away from their long term goals."
Dr Vincent and his co-author and
former student Jordan Skrynka tested 50 participants twice -- once when they
had eaten normally and once having not eaten anything that day.
For three different types of
rewards, when hungry, people expressed a stronger preference for smaller
hypothetical rewards to be given immediately rather than larger ones that would
arrive later.
The researchers noted that if you
offer people a reward now or double that reward in the future, they were
normally willing to wait for 35 days to double the reward, but when hungry this
plummeted to only 3 days.
The work builds on a well-known
psychological study where children were offered one marshmallow immediately or
two if they were willing to wait 15 minutes.
Those children who accepted the
initial offering were classed as more impulsive than those who could delay
gratification and wait for the larger reward. In the context of the Dundee
study, this indicates that hunger makes people more impulsive even when the
decisions they are asked to make will do nothing to relieve their hunger.
"We wanted to know whether
being in a state of hunger had a specific effect on how you make decisions only
relating to food or if it had broader effects, and this research suggests
decision-making gets more present-focused when people are hungry," said Dr
Vincent.
"You would predict that hunger
would impact people's preferences relating to food, but it is not yet clear why
people get more present-focused for completely unrelated rewards.
"We hear of children going to
school without having had breakfast, many people are on calorie restriction
diets, and lots of people fast for religious reasons. Hunger is so common that
it is important to understand the non-obvious ways in which our preferences and
decisions may be affected by it."
