Having an empty stomach leads to poor decisions, new research shows

Making a decision while you're hungry is not advisable according to a new study.

Scientists at the University of Dundee 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 later.

The research suggests being hungry changes preferences for rewards entirely unrelated to food and may carry over into other kinds of decisions such as financial or interpersonal ones.

Dr Benjamin Vincent, who carried out the study, said he believed it was important that people know that an empty stomach might affect their preferences and there was also a danger that those in poverty may make decisions that entrench their plight.

Dr Vincent added: “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 unhealthy or indulgent.

“Our research suggests this could have an impact on other kinds of decisions as well. Say you were going to speak to a pensions or mortgage adviser – 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 foresee and mitigate the effects of hunger, for example, that might bias their decision-making away from their long-term goals.”

A group of 50 participants were tested twice for the study by the university’s psychology department – once when they had eaten normally and once having not eaten anything that day.

When hungry, people expressed a stronger preference for smaller hypothetical rewards to be given immediately rather than larger ones that would arrive later.

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 three 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.

Dr Vincent said: “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.”

The study is published in the journal Psychonomic Bulletin and Review.