Until recently, it was considered that if we desired something, it was because we enjoyed it. But science is now calling that theory into doubt – and opening the road to a viable addiction solution.

In 1970, a crude and terrible experiment was carried out on a mental patient in New Orleans. Patient B-19 is the only name we have for him.

B-19 was dissatisfied. He’d been dismissed from the military for homosexual inclinations and had a drug problem. His psychiatrist, Robert Heath, plugged electrodes into his brain as part of his treatment in an attempt to “cure” him of being gay. The electrodes were attached to what were considered to be the pleasure centres of the brain at the time.

B-19 featured the ability to switch the electrodes on by pressing a button while they were connected. And he pressed it repeatedly – over 1,000 times in a single session.

“It made him feel very, extremely sexually stimulated,” says Kent Berridge, a University of Michigan professor of biopsychology and neuroscience. B-19 had a strong desire to masturbate. He found both men and women sexually appealing while wearing the electrodes. When the electrodes were removed, he moaned vehemently.

However, Robert Heath saw something peculiar. He anticipated B-19 to use words like “great,” “awesome,” and “wonderful” when he asked him to explain how the electrode made him feel. He, on the other hand, did not. In fact, he didn’t appear to enjoy himself at all.

So, why did he continue to click the button, and why did he object when the electrodes were removed? According to Kent Berridge, we must first acknowledge that, despite not like the feelings created by the electrodes, B-19 desired to turn them on.

That, on the other hand, seems like a contradiction.

For many years, psychologists and neuroscientists thought there was no genuine distinction between liking and desiring something. “Liking” and “wanting” appear to be two terms that describe the same thing. Isn’t it true that I desire a cup of coffee in the morning because I enjoy coffee?

There was another presumption that goes along with this one: that desire equals liking. It was commonly assumed that a brain mechanism containing the hormone dopamine was responsible for both desiring and liking.

Furthermore, there appeared to be strong evidence that dopamine is required for pleasure. Rats, like humans, enjoy sugary treats, but when dopamine was taken out of their brains and sweet substances were placed in their cages, they stopped seeking them out. It was assumed that if you cut off the dopamine, you also cut off the pleasure.

Was this, however, correct? Kent Berridge came up with a new technique to look into the relationship between dopamine and pleasure. He fed the rats a sweet solution  “And to our surprise, the rats still liked the taste normally. The pleasure was still there!”

Dopamine levels were elevated in rats in another experiment at his lab, resulting in a massive rise in eating but no obvious improvement in liking.

You might be wondering how a scientist in a lab coat can detect if a rodent is having fun. The answer is that rats exhibit facial expressions that are similar to those of humans. They lick their lips when they consume something sweet, and they open their mouths and shake their heads when they eat something harsh.

So, what exactly is going on here? Why do rats continue to enjoy a food that they don’t seem to want?

Kent Berridge had a theory, but it was so far off that even he chose not to accept it for a long time. Was it conceivable that desiring something and not being able to have it was the same thing? Was it feasible that dopamine had nothing to do with liking and that it was all about wanting?

The scientific community has been sceptical for many years. However, the hypothesis is now widely accepted. Dopamine makes you more tempted. Dopamine motivates me to make a cup of coffee when I walk downstairs in the morning and see my coffee machine. If you’re hungry, dopamine increases your desire for food, and it makes a smoker need a cigarette.

The unlucky laboratory rat provides the most shocking proof that the dopamine system fires desiring and not liking. Kent Berridge affixed a little metal stick to the rat cage in one experiment that produced a tiny electric shock when touched. After one or two touches, a typical rat learns to stay away from the stick.

Berridge was able to make the rat become engaged with the stick by stimulating the rat’s dopamine system. It would approach it, sniff it, nuzzle it, and use its paw or nose to touch it. Even after receiving the mild jolt, it would return repeatedly within a five- or 10-minute period before the testing was stopped.

Wanting, he claims, is more basic than liking. In the end, whether we enjoy sex or eating has little bearing on the maintenance of our genes. The question of whether we want to have sex and eat is far more significant.

The most essential aspect of the wanting-liking dichotomy is the insight it provides into addiction, whether to drugs, alcohol, gambling, or maybe even food.

Wanting separates itself from liking in the addict. The dopamine system learns that particular signals, such as seeing a coffee machine, are associated with rewards.

The dopamine system of the addict gets sensitised in ways that are not completely understood. The desire to have something never goes away, and it is sparked by a variety of factors. A syringe, a spoon, a party, or simply sitting on a street corner might trigger a drug addict’s desire to use narcotics.

But the yearning never goes away – or at least not for a long time. As a result, drug users are more prone to relapse. They want to use the drugs again, even though they don’t get much pleasure from them. Dopamine sensitization can last up to half a lifetime in rats. Researchers must now determine whether they can reverse this sensitization in rats and, perhaps, in people.