How the Brain’s Reward System Changes as Romantic Love Matures
Sunday, February 8, 2026.
A neuroscience study shows why long-term love feels quieter without being weaker.
A new neuroscience study finds that the brain’s dopamine-based reward system encodes romantic partners as less neurally distinct over time—even while passion, intimacy, and commitment remain high.
The research, published in Social Cognitive and Affective Neuroscience, examined how the brain differentiates a romantic partner from close friends, focusing on the nucleus accumbens, a dopamine-rich region involved in reward anticipation and motivation.
The key finding is not that romantic partners are processed differently than friends—that has been shown before—but that this neural distinction becomes less specific as relationships last longer.
Crucially, the change cannot be explained by people feeling less in love.
The reduction in neural specificity remained even after researchers controlled for self-reported passion, intimacy, and commitment.
In other words, the relationship may feel stable and bonded while the brain quietly changes how much effort it devotes to marking one person as exceptional.
How the Study Measured Romantic Reward in the Brain
The study involved 47 heterosexual men between the ages of 20 and 29, all in committed romantic relationships averaging about 18 months in length.
Participants who were married or had children were excluded to avoid confounding long-term domestic or parental dynamics with romantic bonding itself.
Here’s what I found intriguing. Rather than relying on strangers or stock images, the researchers used participants’ real relationships.
Each participant selected three people from his life: his romantic partner, a close female friend, and a close male friend. Each person recorded short video clips displaying either positive social cues—smiling, waving, clapping, or encouraging gestures—or neutral expressions.
While undergoing functional MRI scans, participants completed a social incentive delay task, a well-established paradigm for measuring anticipation of reward.
On each trial, participants were cued to expect feedback from one specific person.
If they responded quickly enough to a briefly presented target, they were rewarded with a positive video from that person.
Slower responses resulted in neutral feedback.
Behaviorally, the results were unsurprising but important.
Participants responded fastest when anticipating feedback from their romantic partner and rated their partner’s positive videos as the most rewarding.
The brain data told the more consequential story.
The Central Finding: Reduced Neural Specificity Over Relationship Duration
To analyze brain activity, the researchers used multivoxel pattern analysis, a technique that examines fine-grained patterns of activation rather than simply asking whether a brain region is more or less active.
This distinction matters.
The question was not whether the nucleus accumbens “lit up” more for partners.
The question was whether the brain encoded partners differently.
Early in relationships, it did.
The nucleus accumbens produced a distinct neural signature when participants anticipated positive feedback from their romantic partner, reliably differentiating that partner from both a close female friend and a close male friend.
The partner was not merely preferred; the partner occupied a separate representational category.
But as relationship duration increased, that distinction softened.
Study subjects who had been in longer relationships showed less differentiation between the neural patterns associated with their romantic partner and those associated with their opposite-sex friend.
This effect remained statistically significant even after controlling for reported intimacy, passion, and commitment.
This is the study’s central contribution, stated plainly:
The brain’s reward system treats romantic partners as most neurally distinct early in relationships and relies less on that distinction as relationships mature.
Not absent.
Not reversed.
Less emphasized.
What the Nucleus Accumbens Is Really Tracking
The nucleus accumbens is often described as a pleasure center, which is how life partners avoid admitting that romance is partly an efficiency problem.
More accurately, this region tracks motivational salience—what the brain anticipates, prioritizes, and is willing to expend effort for.
Early romantic love requires effort. It requires focus, pursuit, and repeated prioritization of one person over many plausible alternatives. Strong neural specificity in the reward system supports that task. It keeps the partner unmistakable.
Once a bond stabilizes, that labor becomes redundant.
The study does not suggest that partners become interchangeable. It suggests that once a relationship no longer depends on pursuit to survive, the reward system reduces the energy it spends insisting on categorical difference.
From the brain’s perspective, this is not loss.
It’s just good accounting.
Why This Neural Shift Feels Like Decline to Humans
From inside a relationship, reduced reward-system emphasis often feels like something has gone missing.
Life partners describe it as a loss of spark, excitement, or automatic desire, and then assume something has gone wrong.
This study suggests a different interpretation.
What fades is not attachment.
What fades is the neurological urgency of differentiation.
The reward system is no longer shouting because it no longer has to.
The relationship is no longer being held together by novelty-based motivation.
It is being maintained by coordination, familiarity, and trust—processes supported by other neural systems entirely.
The mistake is asking dopamine to keep doing attachment’s job.
What This Study Clarifies That Earlier Research Could Not
Previous studies produced inconsistent findings about whether romantic partners activate reward regions more than friends.
This study helps explain why.
Partner-specific reward encoding is strongest early in relationships.
Neural distinction diminishes as relationship duration increases.
The change reflects time, not declining affection.
The study does not contradict earlier findings.
It contextualizes them.
Why This Matters for Long-Term Relationships
This research helps explain why stable relationships often feel quieter without being weaker—and why chasing early-stage intensity is such a common and unhelpful mistake.
The absence of fireworks is not evidence of failure.
It is evidence that the bond no longer depends on novelty to hold.
The brain, more practical than romantic culture, knows when a job is finished.
Frequently Asked Questions
Does this mean romantic love fades over time?
No. Participants reported high levels of passion, intimacy, and commitment even as neural specificity decreased. The change reflects how love is maintained, not whether it exists.
Does this mean partners become “just friends”?
No. The partner remained distinct from friends. The distinction simply required less reward-system emphasis as the relationship matured.
Is this why desire changes in long-term relationships?
Possibly in part. The findings suggest desire becomes less driven by novelty-based reward anticipation and more dependent on other relational and psychological factors.
Should couples try to “get the spark back”?
This study suggests that recreating early-stage dopamine patterns may be the wrong goal. A more useful focus is learning how intimacy and desire function once dopamine steps back.
Final Thoughts
Dopamine is excellent at starting things.
But it’s not designed to maintain them forever.
What this study shows is not the disappearance of love, but the completion of a task.
Once a bond no longer depends on pursuit, the brain simply reallocates its effort elsewhere.
We panic when love gets quieter because we were taught to confuse stimulation with devotion.
Our brains know better.
Be Well, Stay Kind, and Godspeed.
REFERENCES:
Ujisaki, K., Ueda, R., Nakai, R., & Abe, N. (2024). Reduced neural specificity for a romantic partner in the nucleus accumbens over relationship duration.
Social Cognitive and Affective Neuroscience..