Desire is a curious thing.
Some desires can be easily satisfied. We can indulge them and get immediate gratification. Pleasures like a delicious meal, a warm bath or a favorite song are simple to understand—they make us feel good and so we seek them when we need comfort.
Other desires are insatiable. Indulging them only gives fleeting relief from an insistent craving. Satisfaction seems unattainable. This is the realm of addictions and compulsions, or the many other habits and behaviors that can become an unhealthy drain on our quality of life. In the worst cases, this can lead to a state of desperately wanting something that is actively harmful.
As the author Anne Clendening eloquently puts it (Clendening, 2018):
“Addiction, at its worst, is akin to having Stockholm Syndrome. You’re like a hostage who has developed an irrational affection for your captor. They can abuse you, torture you, even threaten to kill you, and you’ll remain inexplicably and disturbingly loyal.”
Why should this be? Why should there be a vulnerability built into our brains that causes us to want things that are bad for us, things that we don’t even like?
Well, it turns out that, at a fundamental level, “wanting” and “liking” are separate functions of the brain.
Incentive Salience
The impulse to seek the things we want is a phenomenon known as incentive salience. This defines how desirable rewards are and how much of our attention they grab.
If we walked into a messy room that had litter scattered around, but also a smattering of gold coins, we would notice them immediately and want to pick them up. If we walked into a room full of people, and a person we liked on was there amongst the crowd, we would notice them immediately and want to talk to them.
The brain’s reward system regulates this process. The system is based around a cluster of cells in the midbrain that release dopamine as a reward signal into many other regions of the brain—most importantly, into the limbic system and the prefrontal cortex.
The popular view of dopamine is that it is a “feel-good” chemical, but in fact, this isn’t really correct. Dopamine is actually a reward prediction signal—specifically, it signals errors in reward prediction (Schultz, 2016).
Dopamine signaling allows us to recognize rewards, learn to associate specific cues in the environments with reward, and (most importantly when it comes to desire) motivate us to seek reward.
Dopamine provides a “wanting” drive.
Hedonic Hotspots
If you give a mouse a taste of sugar water, it makes a characteristic facial expression that shows it really liked the experience. Humans do the same thing. Sweet taste is an inherently pleasurable sensation.
That pleasure response is based in a region of the limbic system known as the nucleus accumbens, and can be mapped specifically onto tiny regions of this already small brain area known as “hedonic hotspots” (Morales & Berridge, 2020). Within these hotspots, the release of two different neurotransmitters—endocannabinoids and endorphins—regulates the pleasure sensation. These hedonic hotspots seem to be the basic unit of “liking” in the brain.
Ordinarily, our wanting and liking systems work together effectively. If you were exploring the environment and came upon a sweet, tasty fruit, it’s a pleasurable surprise that would register as an unexpected reward and trigger a spike of dopamine release. That positive experience would make you want more.
If you find enough of the fruit, you’ll learn to recognize the tree that it grows on, and seek more of them to increase your supply of sugary reward. Eventually, you end up with orchards.
Crucially, though, while wanting and liking are clearly closely connected in the brain, the fact that they have a different neurochemical basis means they can become uncoupled.
Incentive Sensitization
When it comes to addiction, most drugs of abuse act directly on these wanting and liking systems in the brain and derange their proper functioning. One consequence is that the operation of the wanting drive can become massively amplified.
In this scenario, the dopamine-wanting drive becomes sensitized at the same time that feedback from the executive brain in the pre-frontal cortex is weakened, and so the urge to seek the addictive reward becomes unmanageable. Insatiable.
The hedonic hotspots that used to register liking can even reverse operation to signal dislike, but the relentless wanting drive persists, regardless. This runaway wanting phenomenon has been termed “incentive sensitization” and is likely to be an important part of the transition to addiction (Berridge & Robinson, 2016).
Even without those extremes of instability, it’s an everyday experience to find ourselves wanting something that we know isn’t good for us and that we no longer enjoy.
So, if you’ve ever wondered why you can’t stop checking social media even though it leaves you angry and depressed, can’t stop going back to a person who treats you badly, or can’t stop pouring another glass of wine despite the hangover you know you’ll regret, then here’s your answer: Your dopamine wanting system can keep firing long after your liking hotspots have gone quiet.
References
Schulz, W. (2016) Dopamine reward prediction error coding. Dialogues in Clinical Neuroscience. 18: 23–32.
Morales, I. & Berridge K.C. (2020) ‘Liking’ and ‘wanting’ in eating and food reward: Brain mechanisms and clinical implications. Physiology and Behavior. 227: 113152.
Psychology today
