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  1. #1

    Impulsive behavior may be relic of hunter-gatherer past

    Impulsive Behavior May Be Relic Of Hunter-Gatherer Past
    December 9, 2004
    University Of Minnesota

    Drawing on experiments with blue jays, a team of University of Minnesota researchers has found what may be the evolutionary basis for impulsive behavior. Such behavior may have evolved because in the wild, snatching up small rewards like food morsels rather than waiting for something bigger and better to come along can lead to getting more rewards in the long run. The work may help explain why many modern-day humans find it so hard to turn down an immediate reward--for example, food, money, sex or euphoria--rather than investing and waiting for a bigger reward later. The work will be published in the Dec. 7 issue of the Proceedings of the Royal Society (London).

    In experiments with blue jays, David Stephens, a professor of ecology, evolution and behavior in the university's College of Biological Sciences, found that birds presented with a choice of getting a small food reward immediately or waiting a short time for a bigger one could not be trained to wait, even after a thousand repetitions. Many researchers have explained such impulsiveness as the result of the bird "discounting" the value of a delayed reward--that is, instinctively realizing that a reward delayed may be a reward denied because conditions can change while the bird is waiting. But the birds' impulsiveness was simply too strong to explain that way, Stephens said.

    "I think we were asking them the wrong question," he explained. "In nature, they don't often encounter a situation where they must give up a better, but delayed, food morsel when they grab a quick meal. So we designed an experiment that better modeled real life in the wild."

    The new experiments were modeled on how animals encounter and exploit food clumps. The jays encountered one clump at a time and obtained some food from it. Then they had to decide whether to wait for a bit more from the same clump or leave and search for another clump. Not surprisingly, the birds still acted impulsively, preferring items they could get quickly. They considered only the size and wait time for their next reward--never a reward beyond that, even though it may have been bigger.

    What did surprise Stephens was that the birds that went for the immediate reward were able to "earn" as much or more food in the long run as birds that were forced to wait for the larger reward or to follow a mixed strategy. The reason, he said, was that in the wild, animals aren't faced with an either-or choice of "small reward now or big reward later." What happens is that when they find a small bit of food, they don't wait; they just go back to foraging, and they may find lots of little rewards that add up to more than what they would get if they had to hang around waiting for bigger and better.

    "Animals, I think, come with a hardwired rule that says, 'Don't look too far in the future,'" Stephens said. "Being impulsive works really well because after grabbing the food, they can forget it and go back to their original foraging behavior. That behavior can achieve high long-term gains even if it's impulsive."

    The work may apply to humans, he said, because taking rewards without hesitation may have paid off for our foraging ancestors, as it does for blue jays and other foragers. Modern society forces us to make either-or decisions about delayed benefits such as education, investment and marriage; the impulsive rules that work well for foragers do more harm than good when applied in these situations.

    "Impulsiveness is considered a big behavior problem for humans," said Stephens. "Some humans do better at binary decisions like 'a little now or a lot later' than others. When psychologists study kids who are good at waiting for a reward, they find those kids generallly do better in life. It looks as though this is a key to success in the modern world, so why is it so hard for us to accept delays? The answer may be because we evolved as foragers who encountered no penalties for taking resources impulsively.

    "Also," Stephens added, "the National Institute on Drug Abuse funds a lot of studies of impulsiveness. It seems to play a part in addiction. I think anything we can do to understand impulsivity is a plus."

    Stephens' co-authors were Benjamin Kerr, a postdoctoral associate, and Esteban Fernandez-Juricic, who is now an assistant professor at California State University at Long Beach. The study was funded by the National Science Foundation.

    Related Information
    See Born To Explore: The Other Side of ADD which looks at some of the advantages of ADHD, both today and from an evolutionary perspective -- in particular, see the article Hunters, Explorers, and Dreamers on that site.

  2. #2

    Impulsive behavior may be relic of hunter-gatherer past

    Hee! So, what this study is telling us is that some of us (that would include me) are the mental equivalent of a bluejay? :D

  3. #3

    Impulsive behavior may be relic of hunter-gatherer past

    Or, "impulsivity is for the birds"? ;o)

    Actually, you should have a look at the sites I listed under "Related Information" -- the truth is that the hyperfocus that's a symptom of some forms of ADHD can be quite adaptive under the right circumstances. For example, I think there is a higher incidence of ADHD among high tech professionals, where the hyperfocus can be a benefit. In a similar vein, Dr. James Butcher, who does a lot of psychological testing for police officer recruit selection, looks for impulsivity in police officers, for obvious reasons.

  4. #4

    Impulsive behavior may be relic of hunter-gatherer past

    Heh. I'll have to read some of those. I've spent most of my life apologizing to people because:

    1) I didn't hear you.
    2) I heard you, but it didn't register.
    3) I didn't even know you were there.
    4) Yes, I can listen to the television, work on the computer, formulate a plan for my next project, rub my head and pat my stomach...all at the same time. However, I wasn't listening to what you said.

    ;)

  5. #5

    Impulsive behavior may be relic of hunter-gatherer past

    Quote Originally Posted by ThatLady
    1) I didn't hear you.
    2) I heard you, but it didn't register.
    3) I didn't even know you were there.
    4) Yes, I can listen to the television, work on the computer, formulate a plan for my next project, rub my head and pat my stomach...all at the same time. However, I wasn't listening to what you said.
    Oddly enough, that sounds exactly like the teenagers living in my house... except then they blame me and claim I never told them because... oh... I don't know... being over 30 I must be senile...

  6. #6

    Impulsive behavior may be relic of hunter-gatherer past

    My mother has always sworn that I've never emotionally evolved beyond my teens. Now, I know she's right! If only my poor, old body knew the trick! :D

  7. #7

    Impulsive behavior may be relic of hunter-gatherer past

    "Animals, I think, come with a hardwired rule that says, 'Don't look too far in the future,'" Stephens said.
    Can you imagine pets making long-term plans like "Can we schedule a petting session on Wednesday since that's my most stressful time of the week?"
    "What lies behind us and what lies before us are tiny matters compared to what lies within us." ~ Ralph Waldo Emerson

  8. #8

    Impulsive behavior may be relic of hunter-gatherer past

    :o)

    One of the cats does come in if I'm staying up too late at night to meow and whack with with a paw on the leg until I go to bed... she likes to sleep with people... ;o)

  9. #9

    Impulsive behavior may be relic of hunter-gatherer past

    I've often wondered why I am so danged impulsive! I mean, beyond a symtom of some diagnosis. I would much rather worry about the here and now than later. One reason I don't like waiting is because who knows if it will happen? The opportunity could be gone, I could get run over by a truck tomorrow. I don't feel that you can take the future for granted so to me it's a little silly planning for 5, 10, 15 years down the road. I will admit that that's not a good thing in our society. Shoot, it works for me! (I hope :-)

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