It’s 11:30 AM on a Sunday and you’re at that new brunch place you’ve been meaning to try, where you’ve just been informed that the wait will be at least an hour and a half long. Should you stay, or should you go? Based on new research from Johns Hopkins School of Medicine, your decision may be steeped in biological animal theory. Factors like the perceived value of the reward, measured alongside the time and efforts it’d take to get the reward, might all play a role in how long you’re willing to wait.
The new study, published in Proceedings of the National Academy of Sciences, focused on testing the theory of “optimal foraging” in humans. Optimal foraging theory revolves around the idea that “natural selection favors animals whose behavioral strategies maximize their net energy intake per unit time spent foraging,” according to A Dictionary of Biology.
Basically, the theory, which is typically used to describe foraging behaviors in animals towards rewards like food, says that animals are pretty much wired to maximize the rewards they get based on variables including the reward’s worth versus the time and effort it would take to acquire said reward. It’s a situation with parallels to human life— take how long people are still willing to wait to score the much-coveted Cronut, five years after all the original hype, for example.
"Because animals that maximize optimal foraging live longer, in general, and are more 'fit,' traits that support such behavior are highly conserved in evolution and therefore are likely to inform human as well as other animal behavior," Dr. Reza Shadmehr, study co-author and professor of biomedical engineering at the Johns Hopkins University School of Medicine, said in a statement. "We believe that the speed at which an animal moves to the next reward, which we call 'vigor,' is related to this principle in people too."
To test the theory on humans, the scientists conducted an experiment with 92 subjects, tracking study participants' eye movement speed and direction while they observed pictures. Recording the eye movements between the objects presented in the pictures served as an indicator for the subjects’ preferences. Photos of human faces were the high-value “reward,” while inanimate objects (like an image of a door) were the low-value rewards. The scientists documented measures like how long the reward (a face or inanimate object) held the subjects’ gaze and how fast the subjects would shift their focus from one object to another on the computer screens.
What they found was that the theory, for the most part, held true in the experiment. After being presented with numerous low-value rewards (aka doors galore), people tended to increase gaze duration, while the speed of their eye movements decreased (note: this is an involuntary process). Subjects who experienced numerous high-value rewards (lots of photos of faces) exhibited increased eye movement speed to take in all the faces presented, as well as increased gaze duration.
"A history of high effort to reach a reward may make that reward seem much more valuable, and we'll spend more energy to get that reward," Dr. Shadmehr explained.
The research also highlighted that the more valuable (“richer”) a reward is perceived, the faster people might move to get it (which seems obvious to anyone who’s ever tried to snag the last in stock item in their shopping cart during an online sale).
The study results are another step towards unraveling the mechanisms behind reward-oriented human behavior, especially regarding how humans perceive value and make choices based on these perceptions. “The way we identify preference and choice could be measured in part by measuring innate vigor," added Shadmehr.