Napoleon may have been onto something when he noted that "an army marches on its stomach." A new study has found that hunger is a stronger motivational force than thirst, anxiety, fear, and social needs.

A team led by researchers from the National Institutes of Health found hunger to be the most important motivational force in mice. In fact, the team found hunger’s advantage over the other instincts to be so strong that mice would risk their lives to spend more time in fear-evoking locations just to satisfy their hunger. In addition, the team identified agouti-related peptide (AgRP) neurons as playing a key role in establishing hunger as the all-important driving force, and outlined the behavior of these neurons.

For their study, the team conducted a number of experiments such as depriving mice of food and water for 24 hours and then seeing which resource they ran to when given a choice, and putting both hungry and sated mice in dangerous locations and seeing how they reacted. Not only did hunger prove to be a stronger driving force than safety and thirst, but it was also more important than socialization. For example, in one experiment, socially isolated mice were given the choice to spend time in a chamber containing food or a chamber with another mouse. Mice who were sated strongly chose the company of another mouse, but the hungry mice chose the chamber containing food.

“Our continued existence, among that of other species, has motivated us to pursue an array of behaviors, all governed by our nervous system,” Michael Krashes, a researcher involved in the project explained in a recent statement. "Of course, we can't pursue all those motivations at once, so we have had to choose which ones were most important during different times of need.” Animals that consistently picked the “right” motivation over others survived, and over the course of evolutionary history, we are left with creatures motivated by food above all else.

Source: Burnett CJ, Li C, Webber E, et al. Hunger-Driven Motivational State Competition. Neuron . 2016

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