Whether it’s the momentary feeling of bliss in a budding relationship or the profound connection in the deepest of relationships, love is something we have all experienced in one form or another.
The age-old adage ‘love is blind’ suggests that when we fall in love, we become oblivious to the flaws and imperfections of our partners. While this notion may seem merely poetic, there’s a scientific basis behind it rooted in the complexities of human brain chemistry.
Love: an evolutionary perspective
As a scientific theory, evolution describes environments and events that shape our biology to increase our chances of survival as a species. Interpersonal bonds serve as an adaptive mechanism that enhances the survival and further reproduction of a species’ offspring and could explain why love is a ubiquitous and defining human emotion.
During the Pleistocene Epoch — also known as the Great Ice Age — the early stages of human evolution required the forming of strong social bonds beyond mating, which were essential for survival. These bonds allowed food and shelter to be shared to help individuals survive when resources were scarce. Group cooperation aided in the protection from predators and rivals and the collective effort of communities in nurturing offspring ensured the survival of children.
This early mechanism extends into adult relationships, shaping the formation of romantic bonds. Pair bonding is characterized by attachment, trust, and emotional fulfillment, contributing to the experience of being “in love.” For example, mother-infant bonds provide the evolutionary foundation of pair bonding in humans.
Evolutionary biologists argue that choosing partners with different genetic traits can result in healthier children who are more adaptable to their environment. A diverse mix of genes can strengthen the immune system and increase the offspring’s chances of survival.
Other studies suggest that we might prefer seeking partners who possess attributes that complement our own strengths and weaknesses, thereby enhancing the overall fitness of the mating pair. Complementary traits can bind couples together when they have similar ideological values, morals, and shared vision for the future.
Love in Homo sapiens
Human relationships encompass a range of behaviours shaped by both socio-cultural and psychological mechanisms. While stereotypes and gender roles suggest that women are more expressive and nurturing and men more stoic and competitive, human behaviour is far more nuanced. For example, cultural and societal factors heavily influence what men and women deem attractive, and how they select and express love.
In many South Asian cultures such as Nepalese Hindus, arranged marriages prioritize compatibility in socioeconomic status, family background, and religious beliefs. In other countries and social groups, partnerships value individual autonomy and romantic love, which shapes relationship dynamics.
Perhaps you are more familiar with the halo effect, a psychological experience which denotes how individuals perceive their partners positively in one aspect and extend that perception to other characteristics. Individuals enamoured by their partner’s appearance may selectively ignore the negative traits and assume their partner is also kind, intelligent, and trustworthy solely based on initial attraction.
As such, the halo effect can contribute to the perception that love is blind by blurring the boundaries between rational evaluation of qualities and emotional attachment. Evidently, human relationships transcend biological imperatives, reflecting the richness of cultural, social, and individual experiences.
Chemical love: The brain chemicals that underlie our relationships
Recent advancements in neuroscience have attempted to examine the neurobiological reasoning behind love and attachment.
Brain imaging studies have shown that regions associated with reward and motivation are triggered in response to romantic stimuli — such as kissing, cuddling, or enjoying a hobby with your partner — which motivates us to bond with our partners. Moreover, the release of neurotransmitters — brain chemicals that modulate brain function — such as dopamine, oxytocin, and serotonin play a crucial role in bonding and attachment.
When we engage with someone we find attractive or emotionally stimulating, dopamine levels rise, leading to feelings of euphoria, excitement, and intense pleasure. This fosters feelings of closeness and connection.
Interestingly, studies have shown that individuals in romantic relationships, especially early on in the relationship, go through the ‘honeymoon phase,’ and have serotonin levels similar to those with obsessive-compulsive disorder. This finding would support the commonly used expressions where the state of falling in love often makes one ‘lovesick,’ or obsessed with their partners.
In the midst of a budding relationship, our brain is flooded with neurotransmitters which overshadow the areas of our brain that focus on rational thinking and decision-making. As the jitters of the honeymoon phase wane, we are better able to realistically assess our partners.
However, long-term companionate love is characterized by increased activity in brain regions associated with attachment and long-term bonding and increases in hormones such as oxytocin that are more intimately related to attachment and bonding.
What about other species?
Vasopressin — another neurotransmitter associated with relationships — and oxytocin also support social bonding in other species. Studies show that a surplus of vasopressin and oxytocin receptors — proteins that ensure hormones and neurotransmitters are functional — promote monogamous pair bonding in prairie voles — a species of vole native to central North America.
When the release of these chemicals is blocked, this bonding behaviour changes and the animals become more sexually promiscuous. Unlike prairie voles, montane voles — another vole species native to western North America — have fewer oxytocin and vasopressin receptors, explaining their promiscuous behaviour. As a result, unlike prairie voles, montane voles do not develop partner preferences or form attachment bonds.
While current evidence does not strongly support a link between oxytocin and vasopressin receptor densities and human promiscuity, ongoing research in non-human primates offers valuable insights that could inform future studies. These studies suggest that further investigation into the distribution and function of these receptors in humans could create further evidence of the connection between certain chemicals and our romantic behaviours.
Anecdotally, love may be a matter of the heart, but it is in fact the brain that creates the experience of love. From navigating the whirlwind of feelings associated with new relationships to deepening our appreciation for existing relationships, we’re all on a quest for intimacy and belonging. Understanding the science and neurobiology of love provides valuable insights into the complexities of human connection and can help foster better long-lasting relationships.
Tiffany Chien is a Science Writer for the Raw Talk Podcast. This article is influenced by Episode #108 of the podcast, titled “The Psychology of Love and Relationships.”
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