Sex, food and drugs all share something in common: the potency of desire. We can crave, enjoy and seek them out. In the field of psychology, we bucket them under the umbrella term rewards, referring to objects and experiences humans perceive to be desirable. These can either be inherently valued as good (e.g. sex, food or water), or require learning through association (e.g. scrolling, shopping or gambling). The conceptualisation of rewards as pleasurable can be traced back to a classic experiment carried out in 1954 by Olds and Milner. Fifteen male rats with brain-implanted electrodes were placed in an experimental box. Inside the box was a lever which, if pressed, delivered a current to the electrodes allowing the rats to self-stimulate specific parts of their own brains. The rat with the highest score pressed the lever more than 7,500 times in a 12-hour period and the lowest scoring rat did it 3,000 times. When examining the results a realisation emerged; the researchers may have found an area “whose peculiar function is to produce a rewarding effect on behavior”. From this grew the conceptualisation of rewards as something inherently enjoyable and associated with pleasure.

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However, the desire for something is not necessarily linked to the enjoyment of consuming it. This was first suggested by contemporary neuroscientist Kent Berridge, who together with colleagues have outlined a more nuanced way to understand the workings of rewards. They suggest the neurological underpinnings for ‘wanting’ is different from ‘liking’. Most people understand wanting as the conscious desire for a particular thing or action. Usually, as an explicit thought possible to express to ourselves or others, often taking the shape of future oriented sentences (e.g. “I want a higher salary”). It may even be seen as something that lies partly within our control. In the instance of reward processing, the meaning of ‘wanting’ is slightly different. It refers to incentive salience which is the influence on our behaviour to get closer to or consume rewards without necessarily being consciously aware of this. The line between conscious and subconscious is not clear cut. However, the take-away message here is the possibility of wanting things we are unaware of, to the degree that we will get nearer to, or even consume it. Most of the time our conscious wanting and subconscious ‘wanting’ will drive us towards the same destination. Yet, it is possible to desire something that we do not consciously want. For example, someone addicted to drugs who cognitively does not want to consume a substance can still feel pulled towards it or objects associated with it.

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The high from a drug, the release from an orgasm or the sweet taste of ice cream all describe the pleasure aspect of reward. This is called ‘liking’ or hedonic impact, which essentially means the experience of feeling good. Similarly to wanting, liking can be both a conscious experience and a subconscious one. Neuroscientists have managed to identify hedonic hotspots in the brain that give rise to the ‘liking’ response. These areas are interconnected and make up a relatively small neural network. The area called nucleus accumbens (NAc) is central to the brain’s reward system. Structurally, it has a centrally located core and a shell that wraps around parts of it. The hedonic hotspots thought to give rise to the experience of pleasure are located in the shell. This part only takes up 10% of the total volume of the whole structure. The remaining 90% can functionally generate wanting, meaning that we have a greater portion of the brain dedicated to generating ‘wanting’, compared to ‘liking’. If we briefly return to the example of addiction, research has shown that the behaviour of addiction can be driven by the circuits of ‘wanting’ without the person experiencing ‘liking’.

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It is believed that these neurological pathways evolved during the same time, and while they are dissociable, they are also intertwined. Together they are part of generating the association between a given stimulus and the pleasure of it, constituting the basis of reward learning. I find it fascinating that by deconstructing the concept of reward and investigating the underlying neurological pathways, we could better understand something quite fundamental about the human experience of desire.