If you’ve ever felt the pangs of hunger turn into frustration and annoyance, then you’ve likely experienced being “hangry.” The feeling of hunger can cause us to become noticeably more emotional, and even change our decision making. But new research suggests that animals — humans included — can make surprisingly good decisions just based on the food in their stomach.
Led by the University of Exeter, the study found that surviving in difficult and dangerous situations doesn’t actually necessitate a high-functioning brain. What does help is if animals are sensitive to their body condition, such as how hungry they are. Hunger acts as a memory of past food availability, letting the animal know what conditions may be like currently.
The research team, led by Dr. Andrew Higginson of the University of Exeter, used computer modelling to predict how animals would behave to maximize survival when food supply is unpredictable and the environment is full of predators. Their model determined that an animal that bases its decision-making on only its current resources can survive almost as long as one that uses its brain to calculate the best move to make.
“Our model explains why there is link between our gut and our decisions: hunger can act as a memory telling us there’s not been much food around, which it’s important to respond to in the wild,” explains Higginson. “The usefulness of such memory means that animals, including humans, may appear to be processing a great deal of information in the brain when in fact they are just following their gut.”
The authors believe that this simple, physiological form of memory may have allowed animals to negate investing in building brain tissue, which is a major energy requirement. “If it costs a lot of resources to be so clever, then natural selection will have found a cheaper way to make decisions,” posits John McNamara, a professor at the University of Bristol’s School of Mathematics and author on the study. “The ability to use internal states such as hunger as a memory will have reduced the need to evolve big brains.”
Pushing beyond these findings, it seems quite possible that simple memories could also be encoded in other physiological states — emotions, for example. If this is the case, it could explain why it takes a long time to calm down after feeling threatened. The emotion keeps the body in fight or flight mode just in case the threat returns. The authors suggest that our ability to use emotions as “memory” might be why we even have emotions in the first place.
Beyond exploring the physiological implications of these findings, this research also has implications for conservation. “By using their body condition as a cue, the animals in our model can still perform well when the environmental conditions change suddenly,” says Higginson. “This suggests that some species might be able to cope with the effects of climate change better than expected.”