Rat Park - The Rat Park Experiments

The Rat Park Experiments

In Rat Park, Alexander built a short tunnel large enough to accommodate one rat at a time. At the far end of the tunnel, the rats could drink a fluid from one of two drop dispensers, which automatically recorded how much each rat drank. One dispenser contained a morphine solution and the other plain tap water.

Alexander designed a number of experiments to test the rats' willingness to consume the morphine. Rats have a sweet tooth, so in "The Seduction Experiment," the researchers exploited the rats' apparent sweet tooth to test whether they could be enticed to consume morphine if the water was sweet enough. Morphine in solution has a bitter taste for humans, and appears to have the same effect on rats, Alexander writes, since they shake their heads and reject it as they do with bitter quinine solutions. The Seduction Experiment involved four groups of rats. Group CC was isolated in laboratory cages when they were weaned at 22 days of age, and lived there until the experiment ended at 80 days of age; Group PP was housed in Rat Park for the same period; Group CP was moved from laboratory cages to Rat Park at 65 days of age; and Group PC was moved out of Rat Park and into cages at 65 days of age.

The caged rats (Groups CC and PC) took to the morphine instantly, even with relatively little sweetener, with the caged males drinking 19 times more morphine than the Rat Park males in one of the experimental conditions. But no matter how sweet the morphine became, the rats in Rat Park resisted it. They would try it occasionally — with the females trying it more often than the males — but invariably they showed a preference for the plain water. It was, writes Alexander, "a statistically significant finding." He writes that the most interesting group was Group CP, the rats who were brought up in cages but moved to Rat Park before the experiment began. These animals rejected the morphine solution when it was stronger, but as it became sweeter and more dilute, they began to drink almost as much as the rats that had lived in cages throughout the experiment. They wanted the sweet water, he concluded, so long as it did not disrupt their normal social behavior. Even more significant, he writes, was that when he added a drug called Naloxone, which negates the effects of opioids, to the morphine-laced water, the Rat Park rats began to drink it.

In another experiment, he forced rats in ordinary lab cages to consume morphine for 57 days on end, giving them no liquid to drink other than the morphine-laced solution, then moved them into Rat Park, where he allowed them to choose between the morphine solution and plain water. They drank the plain water. He writes that they did show some signs of dependence, but no sign of addiction. There were "some minor withdrawal signs, twitching, what have you, but there were none of the mythic seizures and sweats you so often hear about ..."

Alexander believes his experiments show that animal self-administration studies provide no empirical support for the theory of drug-induced addiction, and that the theory has no other strong basis in empirical science, although it has not been disproven. "The intense appetite of isolated experimental animals for heroin and cocaine in self-injection experiments tells us nothing about the responsiveness of normal animals and people to these drugs. Normal people can ignore heroin ... even when it is plentiful in their environment, and they can use these drugs with little likelihood of addiction ... Rats from Rat Park seem to be no less discriminating."