The richer the reward, the faster you will move to achieve it, study shows


Credit: CC0 Public Domain

If you've been wondering for how long have you been willing to buy this new holiday gift, scientists at Johns Hopkins Medicine say the answer can be found in the biological rules governing how animals usually look for food and other rewards.

They report that the results of a new study in people state the theory known as "optimal foraging," which states that animals are naturally connected to maximize the rewards they acquire based on factors such as the value of the reward itself and the time to reach this reward. They also add evidence that the richer the reward, the faster people will move to get it. In other words, if you buy this incredible gift really matters, you will not only spend more, but you may also run to be the first in line to hold it.

A description of the study was published online on October 15 Annals of the National Academy of Sciences.

"As animals that maximize foraging live longer in general, and are more apt, the traits that support this behavior are highly conserved in evolution and therefore tend to inform human behavior and others animals, "says Reza Shadmehr, Ph.D., professor of biomedical engineering at the Johns Hopkins University School of Medicine. "We believe that the speed with which an animal moves to the next reward, which we call" vigor, "is related to this principle also in people."

To study the vigor of people, Shadmehr and his colleagues tracked the speed and direction of eye movements in 92 people (mean age of 27 years, 51 men and 41 women) while looking at the images on the computer screen. Studying rapid eye movements between objects (movements known as "balloons") is a frequent model for analyzing reward systems, says Shadmehr, because the large number of balloons – 2.5 of them per second, on average – provides an enormous amount of information about our systems. preferences.

On computer screens, scientists displayed images of human faces (which most people prefer to focus on) as high-value "reward" and inanimate objects, such as a door, as the least valuable reward at different places on the screen. They tracked how quickly survey participants shifted their focus from one object to another and for how long the object or face kept their eyes.

In a subgroup of 16 of the 92 study participants, the scientists also controlled the amount of time subjects could see an image of a person's face. As researchers shortened the amount of time to observe, participants moved their eyes, on average, faster between facial images.

"For us, this experience confirms in our people our optimal foraging animal models, which claim that when the environment is rich, animals tend to move faster between the rewards," says Shadmehr.

"Think of children on Halloween," he says, "when they have a relatively short time to investigate a neighborhood known for generous candy donors. Most of them will be running, not by chance, from house to house."

In another experiment with 17 of the 92 subjects, the scientists displayed two images on the screen, sometimes one face and sometimes an inanimate object. When scientists exhibited more faces, participants spent less time looking at an individual face and more time moving their eyes between their faces.

"It tells us that when the environment is rich (ie, more faces), participants not only move quickly between rewards, but spend less time focusing on each individual reward," says Shadmehr. He says researchers have observed this phenomenon among crows on the Pacific coast who forage the beaches for mollusks. They, like human subjects in computer experiments, spent energy digging a mollusk, determining its size and opening it only if it was large enough to be worth the effort.

To the researchers' surprise, Shadmehr reports, an experiment failed to combine current theories of reward and effort. A group of 22 survey participants showed a series of images placed at greater distances on the screen, requiring more extensive eye movements to focus on each image. In other words, the participants had to spend more effort to get their reward. A dot on the screen indicated where the next image would appear.

Conventional wisdom would say that in a difficult environment, animals must conserve their efforts and move more slowly toward the rewards. But the opposite happened. Research participants spent more effort to get their reward, moving their eyes twice as fast between images of any kind as they were farther apart than between the images that were closest.

Shadmehr speculates that unexpected results can be explained by understanding the variations in how some people value certain rewards. "A story of high effort to reach a reward can make this reward look much more valuable, and we will spend more energy to get that reward," says Shadmehr.

Researchers note that there are also differences in vigor among individuals. Some people have twice the vigor of eye movements than others. And the results can vary with age and gender as well. Shadmehr says that most humans have the fastest eye movements at age 14 on average, and that speed slows down with every additional decade of life.

Shadmehr notes that understanding the principles of vigor can do much more than talk about the pursuit of food or fashionable gifts. It can also inform scientists about the conditions that link human movement and cognition, such as Parkinson's disease, a nervous system disease that affects movement and memory, and depression, characterized by slower movements, sadness, and other problems. humor.

Shadmehr also suggests that understanding vigor could promote understanding of economic theory, essentially as we make value choices. "The way we identify preference and choice can be measured, in part, by the measurement of innate vigor," says Shadmehr.

Explore more:
Rapid eye movements: a possible indicator of more impulsive decision making

More information:
Tehrim Yoon et al., Control of movement vigor and decision making during foraging, Annals of the National Academy of Sciences (2018) DOI: 101073 / pnas.1812979115

Journal Reference:
Annals of the National Academy of Sciences

Provided by:
Johns Hopkins University School of Medicine


Source link