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The Rat Park Experiment: Why It Overturned Our Understanding of Addiction

Addiction is a complex psychological and physical process, and approaches to recovery that ignore either the physical or mental components tend to fail. In decades past, it was widely believed that only physical dependency was the root of addiction.

Yet this failed to explain why breaking the physical dependence wasn’t enough to cure the problem. In the late 1970s, scientist Bruce K. Alexander and his associates carried out a study on rats that flew under the radar for years. That experiment was known as Rat Park, and it’s helped us reshape our understanding of addiction in a way that increases the chances of successful treatment.

What Was the Rat Park Study?

Conducted at Simon Fraser University, the Rat Park study was one of the first experiments of its kind to probe into the social and emotional aspects of addictive and compulsive behaviors. The study involved exposing standard laboratory rats to dispensers of both plain water and a morphine solution. Morphine was specifically chosen because it is known to cause a chemical dependency and because the rats voluntarily consumed it with little added sweetener.

The rats were also separated into either the small and empty cages that are the standard for keeping lab rats or added to a very large enclosure known as Rat Park. The population that remained in small cages were further isolated and separated by gender, while the rats living in the cage 200 times the size of a standard environment enjoyed mingling with rats of both genders. They also had toys, free access to food, and other enrichment opportunities that the standard cages lacked.

What Happened?

The differences between the environments were designed to test the hypothesis that social interaction and a richer environment would affect the voluntary consumption of the morphine solution. And in fact, that’s exactly what Bruce Alexander found. His research, published in 1978 in Psychopharmacology, showed that the rats in standard cages took readily to the morphine solution with little encouragement or sweetener.

In contrast, the rats in Rat Park preferred plain water, to an extent that showed a statistical significance. Even when groups of rats were exchanged at 65 days of age between Rat Park and the standard cages, the same patterns of behavior emerged, with relatively the same results across both genders. In a follow-up experiment, even forcing the rats to consume a morphine solution for nearly 60 days did not greatly affect their preference for plain water once introduced into the large and social habitat.

What Does It Mean For Humans?

The Rat Park study was just one limited and somewhat flawed study in the world of addiction research, but regardless of its flaws, it does clearly demonstrate a link between the environment and social fulfillment of an animal and its tendency to choose to use drugs. We can’t apply this directly to humans and say that all addiction is merely environmental because humans and rats do have many psychological differences.

However, it did finally help break the long-standing assumption that addiction is solely chemical and has little to no environmental or social component. That’s why modern addiction treatment focuses on so much more than just helping a person physically break their dependency.


The Rat Park Experiment: Why It Overturned Our Understanding of Addiction

Mike Bundrant

Mike Bundrant is the author of Your Achilles Eel: Discover and Overcome the Hidden Cause of Negative Emotions, Bad Decisions and Self-Sabotage and co-founder at The iNLP Center which offers online certification in Neuro-Linguistic Programming and life coaching.

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APA Reference
Bundrant, M. (2018). The Rat Park Experiment: Why It Overturned Our Understanding of Addiction. Psych Central. Retrieved on January 20, 2019, from


Last updated: 15 May 2018
Last reviewed: By John M. Grohol, Psy.D. on 15 May 2018
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