It took us several centuries to catch on to this and to the power it granted us. In fact, we didn't really begin to work on it until after the catastrophe mentioned in my chapter on our cover story.
Of all creatures the master made, excluding us, you have the greatest freedom of choice. The boss announced, in his first meeting with our leaders after his first plan failed, that we would have to find ways to reduce this freedom if we were to succeed in the social engineering he planned. This didn't turn out to be as hard as we had originally thought. This is because your minds are so puny.
We quickly discovered that your instincts (the pleasurable sensations the master attached to necessary activities such as eating and reproduction) had great power to limit your freedom of choice. You would choose to do things that weren't in your best interest in order to experience the pleasures of those activities. Could we, the boss asked, find ways to increase that pleasure?
Like I said, we didn't really get to work on this until after the catastrophe you brought on yourselves by heeding our suggestion to destroy one of your moons. And the boss was particularly delighted that one of his first projects trapped the very man the master had used to save your race.
Someone in the land animal section of our squad discovered that certain chemicals had the power to slow the operation of your brain. This had obvious effects on your power of choice, which was the first of the brain functions to shut down. One of these chemicals could be easily generated through a simple modification of the single-celled organisms that broke down the sugars in food plants (a process you call fermentation).
Granted, if you consume enough of this chemical (you call it alcohol) your body will slow down to the point of death. That doesn't happen often; usually you just do stupid things your freedom of choice would normally prevent you from doing.
As I've already noted, it is a sign of the weakness of your race that you so quickly become dependent on certain pleasures. You have come to call this process addiction. There are several types of addictions, of course, though they all have the same psychological effect on you. Some involve a desire to continue experiencing the pleasures of your instincts. Others involve a biochemical dependency in which the body itself objects violently to being deprived of the substance to which it has become dependent.
While studying your race, members of the humanity section of the bioengineering squad discovered a chemical in your brains that fit like a key into certain pleasure receptors. These chemicals were generated whenever you did something necessary, such as exercise. The boss immediately ordered the plant life section of our squad to begin developing plants that had chemicals that could imitate this effect.
As time went on, we discovered that we could actually over-stimulate these areas. This produced a hyper-pleasure response in you that led quickly to the biochemical dependency already mentioned. We developed several forms of these chemicals and modified a number of different plants to produce them.
It has been amusing, over the years, to observe the different ways you have developed for delivering these chemicals to your bodies. In some cases you dry the leaves, boil them, and drink the water. In other cases you dry the leaves, crush them, burn them, and inhale the smoke. In recent years you have learned how to extract the effective chemical from the plants or to synthetically manufacture them. These concoctions hold special power over you because of their purity.
That wasn't the limit of our work in the plant kingdom. We have developed a number of other psychoactive chemicals. Some of them speed up the operation of your body systems; others slow those systems down. Still others modify your brains' perceptive functions, providing you with a hallucinatory "trip" into unreality.
Remember, the original goal of these modifications, at least as the boss explained them to us, was to reduce your power of choice. At that they have succeeded masterfully. I have noted, however, that they have some rather undesirable side effects.
First, when a substance has such power over you, you are quite willing to sacrifice things that would otherwise be important to you in order to obtain more of the substance. For a single individual, this doesn't make a whole lot of difference. But in the badly deteriorated remains of the social structure the master first invented for you, the dependence of one individual can mean sacrificing things originally intended to support and sustain others in that social group.
This willingness to sacrifice important things means that people who want to take those things from you need only supply the substance on which you have become dependent. A major portion of your modern economy consists of companies that grow, manufacture, and sell the legal forms of these substances. Another major portion of the underground economy works on supplying the illegal forms. This, of course, provides a ready income for organizations that specialize in illegal activities.
It has become quite a source of humor for us to watch your public policy debates on these issues. You continue to allow the manufacture, sale and use of two of these substances in many different forms, but despite the benefit to illegal organizations and the drain on your law enforcement capabilities, you continue to ban the manufacture, sale, use and even possession of most of the other substances.
(The medical use of these substances is a totally separate issue. It is amusing to us to see the lengths you go to to control these substances, allowing their use for medical purposes, but banning their use for other purposes. The bureaucratic structures you have erected to enforce these rules both deplete your resources and work quite ineffectively.)