Back in 1987, a researcher named Cloninger proposed a classification of two types of alcoholism. With great imagination, he named them as Type I and Type II. Anyway, he said that Type I represented the majority of alcoholics and that it was characterized by four things:
- Late onset (after age 25)
- Low degree of spontaneous alcohol seeking
- Psychological dependence coupled with guilt and fear
- And a low degree of novelty seeking and a high degree of harm avoidance.
That was a pretty astute observation, and, of course, Type II alcoholism was just the reverse: early onset, novelty seeking, and a lot of spontaneous alcohol seeking and not much guilt or fear. What Cloninger didn’t know about back in 1987 was the dopamine reward system of the Medial Forebrain Bundle. If you take a look at these types through the dopamine system, what you see is what you would expect to see from people who had too much dopamine (type I) and too little dopamine (type II). To understand these types better we have to leave humans for a bit and head off with some rat researchers.
It turns out that rats, regular rats that is, don’t really like drinking alcohol. It burns. So to get a rat in a lab to drink alcohol, you have to do what the liquor industry did for my generation; you have to make a wine cooler. You add sugar to the alcohol, and the rats liking for sugar overcomes its dislike for alcohol and it eventually will drink the stuff.
So you start by adding a little sugar and a few of the rats will drink it. As you add more and more sugar, more and more rats will start drinking. Eventually you’ll add enough sugar so that only the very few rats that are most averse to alcohol will not have started drinking. If you line these rats up in the order they started drinking, you get the scientific bell shaped curve (see below). Now you take the rats on the right of the curve (they like alcohol the least) and mate the males and females together. You do the same for the rats on the left of the curve (they dislike alcohol the least). Now you have two new sets of rats — those descended from the left hand of the curve and those descended from the right hand side of the curve. With each of those two groups you do the same experiment, each time taking the extreme right or left and mating them together to make yet another group. So in each generation you get a bell shaped curve, but the curves get farther and farther apart. After about 14 or 15 generations you now have two new strains of rats.

Example of a Bell Shaped Curve
Those rats descended from the right hand side of the right don’t like alcohol at all. They won’t self administer drugs. They just don’t see the point. The rats descended from the left hand side of the curve are very different. They’ll drink straight lab alcohol with no sugar. They love self administering drugs. Read more…