Totally out of control. It's got this life of its own, and I can't tame it any more.

When you take an addictive drug for the first time — nicotine, let's say — a new agent begins to bud around that source of pleasure (i.e., the neurotransmitters that flood your brain while smoking). The agent starts out small and weak. But the more you feed it, the bigger it grows, until there are many neurons, many modules, and even other brain-agents under its influence, feeding off the nicotine and craving it in ever larger doses, co-opting your planning and reasoning skills so it can scheme about how to get more of it.


This process, of course, is extremely adaptive for us, as evolved organisms — but only when the pleasure corresponds to something of survival or reproductive value: food, sex, social status, mastery of physical skills. The fact that our brains are capable of growing agents dedicated to pursuing food and sex is essential to our survival. It's only in the modern (super-stimulating) environment that we get into trouble.


This American Life did a nice segment on addiction a few years back, in which the producers — seemingly on a lark — asked people to personify their addictions. "It was like people had been waiting all their lives for somebody to ask them this question," said the producers, and they gushed forth with descriptions of the 'voice' of their inner addict:


"The voice is irresistible, always. I'm in the thrall of that voice."


"Totally out of control. It's got this life of its own, and I can't tame it any more."


"I actually have a name for the voice. I call it Stan. Stan is the guy who tells me to have the extra glass of wine. Stan is the guy who tells me to smoke."


Note that this isn't literal speech, as in an auditory hallucination. Instead, the 'voice' is simply an agent whose influence is accessible to introspection, and thus capable of being put to words, as an imaginative/interpretive gloss. That we call them voices is simply a testament to the high level of abstraction at which these agents operate.