The Molecule of More

THE MOLECULE OF MORE

eaten. How much ice cream you want has nothing to do with whether
you’re hard-working or  lazy. It’s  just  that  food doesn’t mean as  much 
when you’re not hungry. So the scientists added a new dimension to the
experiment: they manipulated hunger.
The scientists brought in a new group of rats, gave them a good
meal, then  put them through the  experiment. At  all  levels of effort—even 
one single press—the pre-fed rats pressed the lever half as much as the
hungry ones. When the requirement was doubled, they doubled their
efforts. When the  requirement was  quadrupled, they  quadrupled their 
efforts. But  they always stopped at  about one-half the  presses of the 
hungry rats.  They didn’t slack off.  They didn’t give  up.  They just  didn’t 
want to eat as many pellets because they weren’t hungry.
The results reveal a subtle but vital distinction. The feeling of hun-
ger (or the absence of hunger) changed how much the rats valued the
pellets, but it did not diminish their willingness to work. Hunger is an
H&N phenomenon, an immediate experience, not an anticipatory,
dopamine-driven one. Manipulate hunger, or some other sensory expe-
rience, and  you  affect the value of the reward earned through work.
But it’s dopamine that makes the work possible at all: no dopamine, no
effort.
This points us  toward an  understanding of how dopamine affects 
the choices we make between working hard or taking the easy way.
Sometimes we want a fancy meal, and we’re willing to work hard to
prepare it. Other times all we want to do is “veg out”—we’ll tear open
a bag of Cheetos in front of the TV, instead of working for even the few
minutes it might take to make a simple meal. Consequently, the next
step in the experiments was to introduce the element of choice.
The scientists set up a cage with a Bioserve machine and a bowl of lab
chow. The lab chow was bland but freely available—no work required.
To get the much tastier Bioserve tablets, a rat would have to make four
lever presses—minimal effort, but  effort nonetheless. The  rats  with  nor-
mal dopamine went right for the Bioserve treats. They were willing to do
a little bit of work to get something better. The dopamine-depleted rats,
on the other hand, headed over to the easy-access lab chow.