The central nervous system evolved as a tool for rapidly dealing with and adapting to the environment. If we strip down the nervous system’s function to its essential core, it functions as a tool for sensing the surrounding environment and responding with either reward or aversion. As vertebrates evolved this function became increasingly sophisticated, but the essence remains.

Even in the human brain there remain reward circuits that respond to thoughts and sensations by creating a good feeling, and others that respond with an emotionally negative experience. Despite our incredible neurological sophistication, humans are still powerfully motivated by this simple binary system. We seek out pleasant experiences and avoid negative ones. Psychologists have identified a number of cognitive biases, such as cognitive dissonance, that essentially follow this paradigm.

Building a nervous system around reward/aversion circuits is apparently evolutionarily successful, but comes with a significant vulnerability – what if the system can be “hacked”? What if a creature hits upon a behavior that is not advantageous to its survival or propagation, but stimulates the reward circuits? A little bit of this is probably inevitable – incidental behaviors around the edges of those that are truly adaptive. But what if such behaviors take over one’s existence?

That is essentially what addiction is. Addiction can be behavioral, such as gambling or a particular fetish. They can also bypass thoughts and behavior by directly stimulating reward circuits pharmacologically – drug addiction.

I don’t think we are evolutionarily prepared for drug addiction. Animals may encounter edible items in their environment that contain addictive substances, but are unlikely to have access to sufficient amounts that it can be a constant long term behavior. Humans, on the other hand, have figured out how to manufacture large quantities of purified drugs, tweaked to produce a maximal direct stimulation of our reward circuits.

It’s even worse than that, however. A recent study looked at cocaine addiction in a rat model. They found that not only does cocaine use activate reward circuits, driving drug-seeking behavior in the rats, after the rats become addicted the circuits involving negative emotions (involving the central amygdala) become active. Use of cocaine is then necessary to suppress the negative feelings of this circuit.

This study mirrors observations in humans. For many addictive drugs, use creates euphoria and intensely positive experiences. Users are then motivated to seek out this positive experience. Once addicted, however, withdrawal from the substance creates a powerful dysphoria, and users seek out drug use in order to reduce this extremely negative experience. This leads to not just addiction but dependence.

The question is – what are the ethical implications of this research (and yes, this does overlap with the whole free will debate). Can anyone really be blamed because their brains are vulnerable to addiction and dependence? More to the point – neuroscientific research into addiction seems like a powerful argument against legalizing recreational drugs.

At least, it seems to refute the argument that people should be free to choose for themselves if they want to use recreational drugs, because by the very nature of those drugs and brain function, they take away that freedom. Are people who are addicted to a drug really free to choose if they want to keep using that drug? Is it unfair to legalize a pharmacological trap waiting to ensnare the naive, uninformed, or unfortunate?

I know there are potentially practical arguments to be made for legalization, but that is a debate I am not addressing here. I simply don’t buy arguments for drug legalization premised on liberty and freedom, when those drugs by their very nature take away liberty and freedom.

It also seems inevitable that new ways to hack this reward/aversion system are coming. It has already been 50 years since the famous James Olds rat experiment in which an implanted wire stimulating the “pleasure center” of the brain caused the rat to seek out that stimulation to the exclusion of all else, even to the point of starvation.

Direct electrical stimulation may prove more powerful than pharmacological stimulation – and more addictive.

There are more subtle problems coming also. Video game addiction may be a harbinger of more extreme problems to come. What will happen when we can live our lives in a fully immersive virtual reality – when we can create our own reality to maximally cater to our reward centers? Will this be the ultimate trap of our neurobiology?

The deeper conflict here is between living in harsh reality, and making the best of it, vs bypassing the adaptive nature of the reward/aversion circuits in our brain in order to escape to a pharmacologically/electrically/virtually induced fantasy euphoria.