Dopamine and the Mechanics of the Reward System
Dopamine is a neurotransmitter projected from the ventral tegmental area of the midbrain to the nucleus accumbens, the prefrontal cortex, the amygdala, and other regions, and it plays the central role in the brain's reward system. Its function is not simply that of a pleasure chemical, as the popular description suggests. More accurately, dopamine assigns incentive salience: it generates the sense of craving that constitutes wanting, and it drives approach behavior toward the cues that predict a reward. As Kent Berridge's research demonstrated, dopamine is involved in wanting, which is the motivation to obtain a reward, rather than in liking, which is the actual experience of pleasure once the reward has been obtained. The two systems can be dissociated experimentally, so that an animal may continue to pursue a reward it no longer appears to enjoy. This distinction is important in the psychology of romantic love, because the intense craving of the early phase of a relationship, expressed as the urge to see the other person and to be with them, arises from activation of the dopamine system rather than from the amount of enjoyment actually derived from the time spent together. It also explains why early love can feel simultaneously urgent and unsatisfying, since a system built to generate pursuit does not switch off once the object has been reached. Understanding dopamine as the chemistry of wanting rather than of contentment clarifies a great deal about the phase of a relationship in which intensity and stability are hardest to tell apart.
Dopamine Activation in Early Romantic Love
The fMRI research published by Helen Fisher and colleagues in 2005 showed that when people in the early phase of romantic love viewed photographs of their partner, the ventral tegmental area and the caudate nucleus, both dopamine-rich regions, were strongly activated. This pattern of activation resembles the reward response produced by drugs such as cocaine, which provides neuroscientific support for the addictive quality of early love and for the language of craving and withdrawal that people spontaneously use to describe it. The early phase brings a recognizable set of symptoms: intrusive thoughts in which the other person is constantly on one's mind, an intense craving for the next meeting, excessive delight at the partner's most trivial actions, and a diminished interest in anything and anyone else. These changes are generally understood to reflect heightened activity in the dopamine system, which narrows attention onto the cues associated with the reward and devalues competing sources of interest. What is particularly interesting is that this strong dopamine response decays somewhere between several months and several years, after which the relationship moves from passionate love toward companionate love. How long that takes varies widely from one person to another. This transition is also connected to the mechanism of hedonic adaptation, and it results from neural adaptation in which the dopamine response to the same stimulus gradually weakens. The decline is therefore a property of the system rather than a verdict on the partner, which is worth knowing for anyone inclined to read it as evidence that the relationship was mistaken.
Dopamine, Long-Term Relationships, and Compatibility
There are individual differences in the activity patterns of the dopamine system, and these influence romantic behavior and compatibility. Individual variation in the sensitivity of the dopamine system is often discussed in connection with novelty seeking and sensation seeking, and links to the Big Five traits of extraversion and openness have been suggested. Helen Fisher proposed a model classifying personality into four neurochemical types, in which the dopamine-dominant type, which she called the Explorer, is curious and adventurous and tends to be drawn to others of the same dopamine-dominant type. This is Fisher's own model, however, rather than a classification that has been widely validated. For long-term relationships, the practical question is how the dopamine system can be reactivated once the initial response has adapted away, and novel shared experience is the effective answer. Research by Aron and colleagues showed that when couples take up new activities together, such as a new sport, travel, or learning something unfamiliar, relationship satisfaction improves. This finding is consistent with self-expansion theory, and the mechanism runs through novelty promoting dopamine release, with the resulting pleasure being attributed to the relationship with the partner rather than to the activity itself. The attribution is what makes the effect durable, since the partner becomes associated with the experience of expansion. How strongly you and your partner are drawn to novelty is rarely the same, and the gap is easy to misread. When one of you keeps proposing trips or new classes and the other keeps declining, that is usually a difference in appetite for novelty rather than a difference in how much either of you cares. Neither appetite is the flaw that needs fixing. Before concluding that the spark has gone, add one thing neither of you has done before.