Until recently, Thanksgiving Day was sacred. Retailers kept their doors closed until midnight, so the boundary between dignified family dinners and frenzied bargain hunting remained inviolate. Walmart breached this rule in 2011, announcing that its holiday sales would begin at 10 P.M. on Thanksgiving Day. Sears and Kmart followed suit. The following year, Walmart began its sales at 8 P.M. on Thanksgiving Day. And now Walmart has announced that its sales this year will begin at 6 P.M. on Thanksgiving—with many of its online sales having already started almost a week earlier, on the Friday before Thanksgiving. This trend is known as “Black Friday creep,” and it continues because large retailers recognize that many of their consumers are impatient to begin shopping.

Scientists have wondered for some time what makes certain people—and certain species—more patient than others. Eleven monkeys delivered part of that answer in an experiment in 2005. Some of the monkeys were common marmosets, and the others were cotton-top tamarins. The two species share many similarities. They’re both very small, weighing about as much as a tub of margarine. Their brains are small, too, accounting for about two and a half per cent of their body mass. They live in the lower and middle canopies of large trees in South American rain forests, where they’re raised by both of their parents. But tamarins are impetuous while marmosets show restraint. During a series of trials, the monkeys had a choice: they could pull a lever that immediately released two pellets of food, or they could pull a second lever, which would reveal a richer reward of six pellets, but only after a delay. The delay varied across the trials, which allowed the researchers to calculate how long the monkeys were willing to wait, on average, for the bonus pellets. The tamarins were willing to wait an average of just eight seconds for the bonus pellets—any longer, and they pulled the lever that revealed the meagre, two-pellet prize. In contrast, the marmosets were willing to wait an average of fourteen seconds for the bonus pellets, almost twice as long as the tamarins were willing to wait. When the tamarin has long since given up on the bonus pellets, the marmoset waits patiently and comes away three hundred per cent richer.

What is it about marmosets that endows them with twice the patience of tamarins? For all their similarities, the two species have a very different relationship with food. Most of the time, tamarins eat insects. Insects move quickly and spend no more than a few seconds at a time exposed to the gaze of hungry predators. Patience just isn’t a virtue in the world of an insectivore, where waiting means skipping dinner. Marmosets, on the other hand, eat very few insects, preferring instead the gummy sap that flows from tree bark. After scratching at a tree for several minutes, they’re rewarded with a few precious drops of sap. Researchers have argued that these vastly different foraging experiences explain why the monkeys show different degrees of restraint in the lab. The implication here is that patience is learned rather than endowed; a monkey gets better at waiting when he waits more often, just as a weightlifter becomes stronger the more he lifts weights.

Humans who are chronically forced to wait acquire a different skill: they learn to seize fleeting opportunities. In a paper published in 2011 by the Journal of Consumer Research, Kurt Carlson, of Georgetown University, and Jacqueline Conard, of Belmont University, described the political aspirations of Thomas Zych, a write-in candidate during the 2004 U.S. Presidential elections. Zych’s surname had placed him at the end of alphabetical lists beginning in preschool, and continuing through high school and college. He was forced to sit in the back row, for instance, and he sometimes missed out on the privileges that were offered first to the Abels and Andersons but never quite reached the Zuckermans and Zolas. Zych’s Presidential platform was simple: to abolish alphabetical lists from every sphere of life.

Those years of waiting made Zych hungry enough to stage an anti-alphabetism campaign that could never succeed. In fact, there’s evidence that hunger isn’t unusual among people with late-in-the-alphabet names. When Carlson and Conard offered a limited supply of free basketball tickets to a pool of M.B.A. students, those with surnames at the beginning of the alphabet (from A to I) took, on average, longer than twenty-five minutes to respond; those with surnames at the end of the alphabet (from Q to Z) waited an average of only nineteen minutes. Later, the researchers offered a second pool of students the chance to participate in a study in exchange for cash and a bottle of wine. The A-to-I students waited an average of six and a half hours to respond, whereas the Q-to-Z students waited an average of five and a half hours. Years of privilege seemed to have made the A-to-Is complacent, while years of waiting had made the Q-to-Zs hungry.

Several years ago, my colleague Eesha Sharma and I wondered whether financial hardship might change how people respond to attractive products with limited availability. In one of our experiments, students at New York University’s Stern School of Business told us how they felt about their own financial positions relative to their peers’. While the students completed the experiment, we placed a small bowl of M&M’s nearby. We made sure that the bowl was filled mostly with one color of M&M’s, with only a small number of pieces of a second color. While the students who described themselves as privileged ate the M&M’s indiscriminately, choosing an equal proportion of each color, the self-described deprived students rushed to eat the scarce M&M’s. When you remind people that they’re deprived, they become drawn to whatever happens to be scarce nearby, as though possessing a scarce object corrects the imbalance.

Of course, nature also plays a role in determining how people respond to scarcity, as do a number of other factors. Yet a lifetime of waiting also appears to teach you to snatch fleeting opportunities that other people might ignore. Walmart, Sears, and Kmart know that many of their consumers share the hunger of Presidential candidate Thomas Zych and the N.Y.U. students in our study who felt financially deprived—and so Black Friday creep continues.

Adam Alter is the author of “Drunk Tank Pink: And Other Unexpected Forces That Shape How We Think, Feel, and Behave,” and an assistant professor of marketing at New York University’s Stern School of Business. Some of the ideas in this article are discussed in modified form in “Drunk Tank Pink.”

Photograph by Daniel Acker/Bloomberg via Getty.