In the 1930’s psychology was dominated by the behaviourist school of thinking. This facet of psychological thought is based on the premise that all behaviours are maintained and learnt, or rather conditioned, either through positive or negative reinforcement i.e. an elicited behaviour must be followed by a reward for it to be repeated. B.F. Skinner, a prominent behaviourist, devised an operant conditioning chamber, or a “Skinner box,” in which a lever press by an animal either garnered a reward, such as food, or halted a punishment, like that of a continuing shock. Rats, who were placed within this chamber, would soon learn to associate a stimulus, such as a tone, as a cue to press the lever to either be positively reinforced, with a reward, or to stop a punishment and have the behaviour negatively reinforced. In a nutshell, rats learnt to either associate a behaviour with gaining a reward, or averting a punishment, with both outcomes motivating the rat to replicate the behaviour e.g. a lever press.
Skinner suggests that most of our behaviours only become repeatable and learnt through the process of reinforcement; in other words, a behaviour must be rewarded — or, in the case of negative reinforcement, a punishing stimulus must be taken-away — for it to continue. For instance, setting your alarm early every morning for work, Skinner would argue, is a behaviour that has become reinforced because of the rewards it evokes (I mean, who wakes up early for the sake of it?). The work you do may entail positive rewards, such as a salary, recognition, appreciation and it may even give you meaning, all of which reinforce the behaviour and motivate your continued setting of a dreaded morning alarm. These above-mentioned processes of positive reinforcement rely on a common experiential thread: pleasure from reward. But, what mechanism in the brain governs this experience?
In 1954, James Olds and Peter Milner of McGill University, reinvented the “Skinner box” to include the induction of direct brain stimulation — instead of a food reward — when a lever press occurred. Olds and Milner sought to identify a “reward centre” within the brain that was sufficient, when electrically stimulated, to reward the lever pressing behaviour in and of itself. The common-place lab rat was again recruited, with the addition of an electrode inserted into its brain. Olds and Milner imbedded the electrodes into a multitude of different brain regions and tested whether the stimulation of these various regions subsequently resulted in an above average level of lever pressing. They presumed that an increased rate of lever pressing reflected a brain region, when stimulated, that invoked pleasurable sensations. The results were phenomenal: when electrodes protruded into the midbrain, stimulating what is known as the mesolimbic pathway, rats would engage in 5-6,000 lever presses an hour, often at the expense of consuming both food and water. Imagine a feeling of pleasure, so desirable and encapsulating, it even depreciates the motivation for such fundamentals like that of food – that’s what these rats were experiencing.
I know what you’re thinking, sign me up, right? But wait, there’s more.
The mesolimbic reward pathway (see figure 1) — which includes a subset of regions known as the ventral tegmental area (VTA) which projects communicative structures, known as axons, to the nucleus accumbens (NAcc) — carries information concerning reward, using a chemical called dopamine (DA).
To prove DA is about reward, researchers put rats, again, in the famous Skinner box, with another alteration — when rats press the lever, amphetamine, a dopamine facilitator, is injected into this reward system; the result: the lever pressing behaviour becomes overtly continuous. Dopamine, to our brains, is thus synonymous with reward.
The VTA and NAcc also appear to be consistently active, and releasing DA, when we engage in such pleasurable activities like sex, eating and even aesthetic interests, such as listening to music. For example, Salimpoor & colleagues of McGill University measured the mesolimbic pathway activity, and therefore the inferred magnitude of DA release, of participants listening to new music; they found that participants with a greater mesolimbic response were actually more likely to buy the music after having listened to it! Thus, DA appears to be a multi-purpose, reward inducing chemical, responsible for our feelings of pleasure and our motivation for action.
Dopamine certainly has an impressive set of accolades: it governs how rewarding we deem a piece of music — and then how motivated we’ll be to buy that music — as well as if the consequences of a behaviour are pleasurable enough for it to be learnt and reinforced.This internal chemical of ours, however, is also the enforcer of both addiction and, perhaps surprisingly, the online-shopping market.
We’ve already established that a rat will press a lever thousands of times per hour to self-stimulate the reward pathway. Rats will engage in this behaviour even at the detriment to their own survival and during the induction of pain. A rat, to re-experience this level of induced pleasure, will run across an electrified grid, shocking themselves in the process, to press the lever. What begins as a pleasurable experience, motivating the learning and replication of a behaviour, quickly becomes self-destructive.
Dopamine, when released by the VTA, usually stimulates neurons within the NAcc by binding to specific docking sites. DA, however, after leaving the docking site usually purchases a return ticket for a specialised transporter (like when travelling on the London underground) back to the VTA. Introduce cocaine, however, and this return journey becomes blocked (the trains are currently severely delayed, sorry for the inconvenience this may cause to your journey), giving rise to an immense state of euphoria — Resulting from DA continuously stimulating neurons within the NAcc. Administer cocaine into the mesolimbic pathway at a high enough dose, and what will follow is an increased stimulation threshold that weakens dopamine’s effects on the NAcc, making it harder for us to experience pleasure from things we would usually enjoy. In other words, the NAcc has built-up a tolerance to DA.
Koob, director of the National Institute on Abuse and Alcoholism, has shown that this DA reward threshold increase can persist to upwards of a week. Koob argues, that it’s this increase of the DA threshold that causes the feelings of general lousiness that are associated with the experience of acute withdrawal, or, what some experimental adolescents call, the comedown from a high.
The initial mesolimbic DA response to the ingestion of cocaine, consequently, creates euphoria and a strong motivation to repeat this drug administering behaviour. Couple this with an increased DA reward threshold, making it harder for your brain to ascertain pleasure from regular experience and what you’ll get is the comedown. This creates a negative experience: an experience which can only be overcome, quickly at least, by exposing your brain to more cocaine — and the cycle persists.
Seeking out and paying the cocaine supplier, therefore, has become the addicts form of maladaptive lever pressing. What’s that saying? “Too much of something is always bad for you.”
Dopamine, upon first glance, seems to be the chemical that supplies experiential pleasure to rewarding stimuli at the point of use; spoiler, the first glance is wrong.
Place a monkey in a room where she’s learnt time-and-time again that a light signals the beginning of a reward trial — requiring her to press a lever ten times to get a raisin — and something interesting happens to the ordinary DA response. She has participated in this reward scenario enough that, upon getting the raisin, there’s only a miniscule elevation of DA in comparison to elevations observed in the previous trials. Yet, when the light first appears, before any lever pressing has commenced, a slew of DA floods the reward pathway and stays there throughout the lever pressing exercise, with DA levels only falling when the reward is received (see figure 2). Brian Knutson of Stanford University, found something similar in humans, showing that the mesolimbic pathway garners more activity in the anticipation of receiving a monetary reward, than when getting the reward itself.
Thus, once a behaviour has been sufficiently reinforced, it appears dopamine becomes less about reward and more about the anticipation of gaining a reward.
Susan Weinschenk, a Behavioural Psychologist, in her book titled 100 MORE Things Every Designer Needs to Know About People, postulates a link between the anticipatory dopamine release and the advancement of mass-participation in online-shopping. She suggests that, when you indulge in online consumption, as opposed to shopping in-store, you must obviously wait for your products to arrive. This waiting, Weinschenk argues, produces the same anticipatory dopamine spike as seen in the monkeys. Meaning, the anticipation you feel waiting for that Amazon delivery, is fuelled by dopamine.
Indeed, evidence seems to appropriate this idea. A report entitled Digital Dopamine documented the preferences of shoppers from the UK, US, China and Brazil. The report found that, from 1,680 responses, “Seventy-six percent of people in the US, 72 percent in the UK, 73 percent in Brazil, and 82 percent in China say they are more excited when their online purchases arrive in the mail than when they buy things in store.” It appears we’ve become bored of traditional in-store shopping, and now much prefer the dopamine kick we get from ordering online, then waiting in anticipation for our shopping to arrive.
So, in theory, Amazon should thank dopamine for its rise in prominence, or should at least give the chemical a free subscription to Amazon Prime.