The Addicted Brain Read Online Free Page B

behaviors and strange grimaces. On the following morning, they were cross and dismal;they held their aching heads with both hands and wore a most pitiable expression. When beer or wine was offered them, they turned away with disgust, but relished the juice of lemons. An American monkey, an Ateles, after getting drunk on brandy, would never touch it again, and thus was wiser than many men.” (From Charles Darwin’s
On The Descent of Man
, Penguin Classics, pp. 23–24)
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    Today Google, YouTube, and other websites permit all of us to see what our forefathers must have noted in nature: wallabies munching opium-ripe poppies, tree shrews seeking out fermented palm nectar, and even more examples of animals taking advantage of human brews carelessly left sitting around. Unfortunately for modern man, however, the attraction to alcohol, like attraction to food, can go awry in a world where both are easy to get.
Uncertain or Nonregular Rewards Are More Addicting
    What if every lever press doesn’t result in a drug hit, but rather about every third? As psychologists have discovered, and as any gambler knows, an occasional payoff serves as a stronger reinforcement of a given behavior than does an entirely predictable payoff.
    Experiments on food reinforced behavior in the 1950s showed this nicely. Rats traversed a runway to get food as a reward. One group was given a food reward every time they moved down the runway. In another group, there was a reward only about 30 percent of the time. Both groups learned to run down the runway in expectation of a reward. Then the food reward was eliminated for both groups, but they were still allowed to run down the runway in search of it. Now you would expect that the rats wouldn’t give up immediately. They would continue down the runway in subsequent trials even if they were disappointed the previous time, and that’s just what they did. Now here’s the interesting part. The animals that received rewards only 30 percent of the time persisted in the runway behaviormuch longer than the rats that were rewarded each and every time (see Figure 2-2 ). They tried for a longer time. A nonregular reward was more reinforcing and shaped seeking behavior more strongly than the regular reward, whereas actually, the opposite might be expected. We seem to want rewards that have been uncertain or not regular more than we do certain, regular ones!
    Figure 2-2. Nonregular or uncertain rewards are more addicting or reinforcing. Rats were trained to run down a runway for food. One group was rewarded with food every time, and another group was rewarded only 30 percent of the time. Then the food reward was removed completely. The group of rats that had been rewarded each and every time (100 percent of group) gave up or extinguished their running behavior more readily than the rats receiving a reward only 30 percent of the time. The 30-percent group persisted in running down the runway for longer times and more trials, even though there were no rewards. (Adapted from Figure 4.25 from
Psychology
, First Edition, by Henry Gleitman. Copyright © 1981 by W.W. Norton & Company, Inc. Used with permission of W. W. Norton & Company, Inc.)

    This has important implications in our everyday life, where, for example, we may want to shape the behavior of a pet. Suppose a dog begs for table food, and you restrain yourself but nevertheless give in every so often. Although you tell yourself that you don’t do it all the time, and you think you are doing well, you are in fact making it harder for the dog to stop begging. We can easily think of similar scenarios with children, students, and so on. This should give us insight into our own behaviors. Is this why some of us find gambling such a persistent urge?
Animal Model Extended
    The animal model of drug self-administration (see Figure 2-1 ) has been critically important for research in drug addiction. Interestingly, our appreciation of the model has continued to evolve. By