Author Johann Hari has written a book about addiction and the war on drugs, but it wasn’t the book he thought he was going to write. According to his research, a state of addiction might actually have relatively little to do with chemical slavery:

Put a rat in a cage, alone, with two water bottles. One is just water. The other is water laced with heroin or cocaine. Almost every time you run this experiment, the rat will become obsessed with the drugged water, and keep coming back for more and more, until it kills itself.

The advert explains: “Only one drug is so addictive, nine out of ten laboratory rats will use it. And use it. And use it. Until dead. It’s called cocaine. And it can do the same thing to you.”

But in the 1970s, a professor of Psychology in Vancouver called Bruce Alexander noticed something odd about this experiment. The rat is put in the cage all alone. It has nothing to do but take the drugs. What would happen, he wondered, if we tried this differently? So Professor Alexander built Rat Park. It is a lush cage where the rats would have colored balls and the best rat-food and tunnels to scamper down and plenty of friends: everything a rat about town could want. What, Alexander wanted to know, will happen then?

In Rat Park, all the rats obviously tried both water bottles, because they didn’t know what was in them. But what happened next was startling.

The rats with good lives didn’t like the drugged water. They mostly shunned it, consuming less than a quarter of the drugs the isolated rats used. None of them died. While all the rats who were alone and unhappy became heavy users, none of the rats who had a happy environment did.

What’s particularly interesting about this is how well it backs up other research about the importance of our environment. We are more creative when we feel comfortable but are bombarded with different perspectives (cities, busy buildings). We are more criminally inclined when the setting seems to justify it (broken windows, boarded houses).