When humans are looking for something to eat, something in our brains seems to be pushing us towards junk food. This is what some scientists call the ‘optimal foraging theory’, and it shows that our spatial memory, or our ‘cognitive map’, has evolved to prioritize the snacks that are most valuable in calories.
To our hunter-gatherer ancestors, who never know when their next meal will come, this mental ‘drop pin’ will likely come in handy. For modern people tearing up their kitchens, new research shows that sometimes it can be a curse.
A test of spatial memory among 512 participants has now provided direct evidence that human spatial processing is implicitly biased towards high-calorie foods.
When going through a food maze, participants were more likely to remember the location of chocolate brownies and potato chips than healthy foods such as apples and tomatoes.
In the natural world, animals usually seek high-energy food first, but whether humans have this same drive, and whether it involves a higher level of cognitive processing as opposed to reflexes is debatable.
In previous studies, participants quickly categorized and memorized images of high-calorie and low-calorie foods, and brain imaging revealed high-calorie foods reliably involved the reward processing area.
In 2013, small learn among women found improved spatial memory for images of high-calorie snack foods, compared to pictures of fruit and vegetables. This bias also predicts participants’ BMIs, leading the authors to suggest our spatial memory, which evolved over a long period of time, might contribute to unhealthy eating and current weight gain.
New research adds to this idea, and provides evidence the cognitive system is “optimized for energy-efficient foraging.”
In a maze-like room, study participants followed a specific route, sniffing and testing the flavors of 16 foods, sweet and savory, and high and low calorie.
For half of the sample, the volunteers could only smell the food, while the other half could actually taste it as well as smell it. Importantly, no one was told that they would be tested on their spatial memory later.
However, when they remembered fast food it was roughly 27 to 28 percent better than healthy foods, and this was true even after the researchers controlled for other potentially ruling out decisions such as a person’s familiarity with food, the taste of the food, and their explicit desire to consume it. The ratio of protein to fat from these foods is also balanced to stop people from making nutritional decisions.
Even when only smells were available, participants were very good at implicitly ‘knowing’ the calorie content of the sample; In fact, they were one percent more accurate at mapping the locations of high-calorie foods than in taste tests.
Smell and memory are thought to be closely linked in the brain, but humans’ sense of smell is often seen as inferior to other foraging mammals.
“However, our observations demonstrate an individual’s intact ability to distinguish between different odor types, infer the caloric nature of signaled foods from odor cues, and localize odorous objects in outer space,” the authors. write.
“Indeed, a well-developed sense of smell is thought to have provided a survival advantage to the hunter-gatherer (ancestors).”
Our memories may very well be shaped by our unexpected need for food in hunting and foraging, but it is too early to say how these cognitive processes affect our current behavior and food choices.
More research is needed, as currently, there is a lack of literature on high calorie spatial memory and its behavioral effects in modern environments.
Small learn by some of the same researchers, for example, found a spatial memory bias for high-calorie foods, but their findings did not show a clear effect on actual eating behavior.
However, if this theory of optimal foraging is proven correct in humans, it may help explain why it is so difficult to make healthy eating decisions in the modern world.
“The enhanced memory for high-calorie food locations can make high-calorie choices relatively easier to obtain in diverse food environments, particularly for those with greater expression of bias,” the authors. write.
“In this way, cognitive bias can facilitate high-calorie food choices, by taking advantage of an individual’s tendency to choose items that are convenient and accessible when making food decisions.”
Thanks a lot, brain.
This study is published in Scientific Reports.