If you're a pigeon in Leonard Green's lab, pecking at a green light gets you a tasty food pellet immediately. Pecking a red light means waiting - and oh, how eight seconds can try a pigeon's patience. But then the chute opens and you're rewarded handsomely - 30 pellets!
Which do you choose? Most of the time, the green light. For a pigeon, it seems, a bird in hand is worth at least five in the bush.
People, of course, aren't so different, and Green, a Washington University psychologist, can prove it with laboratory experiments on people, rats and pigeons.
Green studies "discounting." That's the tendency for all animals to take a smaller reward sooner, rather than a larger reward later.
"It's something fundamental to what it means to be a living creature," said Amy Odum, a Utah State University psychologist who also studies discounting. "We are very much creatures of the now and driven by immediate outcomes."
And so it will be no surprise if the winners of last month's Powerball jackpot elect a lump sum payout of $121 million - rather than the full $254 million in an annuity paid out over 29 years. Of 43 Powerball jackpot winners from 2003 to 2005, all but two took the immediate payout.
"From an economic perspective, we behave irrationally," Odum said. The overall jackpot is what the cash payout earns at a compounded interest rate of 5 percent over 29 years.
Some financial planners would say that, given inflation, a well-invested lump sum payout could outperform the annuity. But lottery officials say that the low risk and tax advantages of the annuity - the state doesn't pay taxes and can therefore invest the entire principal - make the annuity an overlooked option.
In contemporary culture, Green sees marketers competing to exploit our impulsiveness or appeal to our self-control. It's a war between the payday loan shops and the human resources rep begging you to sign up for automatic 401(k) deductions; between the salesman offering a no-money-down gas guzzler right now, and the scientist telling you that global warming will be a really big deal for your grandchildren - later.
"We have a bias toward the present," said Patrick McAlvanah, a Washington University economics graduate student who also works in Green's lab. "Don't ask people to save when they get their paycheck. You force them to save when they have their long-term interests in mind."
The research is also relevant to addictions. Studies already show that addicts tend to be impulsive. Green is conducting experiments that ask the questions: Do addicts discount their drug of choice more than other things? Do overeaters discount food the same way smokers discount cigarettes?
And the science has practical applications. For instance, Green thinks smokers would have more success quitting if they understood how discounting changes their mind.
In the morning, the long-term value of not smoking can seem strong. But as evening rolls around and the symptoms of withdrawal kick in, the smaller, more immediate pleasure of nicotine outweighs the value of not smoking.
Therefore, Green says, addicts should put themselves in situations where they're immune to the later temptation. Amanda Calvert, another graduate student, calls it "Ulysses tying himself to the mast of the ship," a reference to the legendary Greek hero who bound himself to the mast to avoid the seductive song of the Sirens.
In Green's lab experiments, people, pigeons and rats all display impulsive behavior, but there are differences of degree. Children are more impulsive than adults. Rats are more impulsive than children, and pigeons more than rats.
Warren Bickel, a psychologist at the University of Arkansas Medical School, says self-control and forward-thinking are associated with activity in the brain's prefrontal cortex.
In primates, the size of prefrontal cortex is correlated with sociability - with humans having the largest clan sizes. The implication, he says, is that the human ability to control impulsiveness evolved hand-in-hand with civilized society and our trust in a stable future.
Today, Green says, impulsiveness varies with culture and socioeconomic levels. Wealthy people are less impulsive, for instance, because they have no immediate economic needs.
In some cultures, children are told that "slow and steady wins the race." Other cultures use the proverb, "A bird in hand is worth 10 in the tree," indicating an even more severe level of discounting.
While some consider impulsiveness a bad trait, Green cautions against value judgments. "I wouldn't argue one is right and one is wrong. It's whatever is appropriate to the circumstances," he said.
For most of human pre-history, the future was drastically uncertain. Death arrived capriciously. Cave men didn't worry about their retirement. Impulsive behaviors were likely the best way to ensure living another day.
And if human lives were full of uncertainty, pity the poor, impulsive pigeon, dependent on the filthy forage of city streets. No wonder pigeons peck - just in the hopes that food might lie under their beaks.
In Green's lab, Pigeon No. 15 has finished its hour of forward thinking, or lack thereof.
Calvert opens the experimental cage and holds out an empty two-quart, plastic pitcher. The pigeon gives it a cockeyed glance, then jumps in headfirst, wedging itself in what Calvert calls a "big hug." Calvert totes the cooing pigeon, its posterior hanging out of the pitcher, back to its normal cage.
Pigeon No. 15 would have received more food if it was more patient. But you could also say it had an hour to pig out on fast food, and, after dinner, got a free ride home.
As Odum says, it's all how you look at it: "You can turn impulsivity around and call it spontaneity."