You know when they say, ‘head over heels’ in love? Turns out, that’s exactly it, says Dr E S Krishnamoorthy. “Everyone thinks they’re following their heart, but really, it’s the brain behind the wheel.”
Hang on, let the good doctor explain — he’s a neuropsychiatrist after all, so he’s got a head for this stuff.
“When you’re attracted to someone, your brain first releases cortisol, the stress hormone,” he says. Racing heart, sweaty palms — they’re all signs your body thinks it’s a crisis, aka love.
While cortisol floods the system, serotonin, the neurotransmitter responsible for rational thought, dips, leading to obsessive thoughts about the person (hence, falling ‘madly’ in love). This is the stage of lust, passion, wild attraction.
Next, dopamine, released from the hypothalamus, kicks in. “You’re not deeply in love yet, but dopamine makes everything — kissing, touching — pleasurable and addictive, like a drug,” says Dr Krishnamoorthy. This phase also marks the transition from attraction to intimacy. “Passion fades once the reward centre is satisfied, which is when partners may stray, much like an addict chasing the next high.”
A subject so fascinating that Dr Krishnamoorthy is hosting a lecture on the science of love, featuring 15 paintings from the 15th century onward, at Udhbava: The Museum Studio in Chennai on Saturday (also online). He uses the 1817 painting Love and Psyche by Jacques-Louis David, for instance, to represent stage three, romantic love.
This phase, following intimacy, involves chemicals such as oxytocin (the ‘cuddle’ hormone released during a hug) and vasopressin, both of which deepen attachment, calm and long-term bonding after sexual contact. “They are linked to monogamous relationships, where there is a shift from risk and excitement to comfort and security.”
Just as love endures, so does research on it, apparently. Nine years ago, Chennai-based Dr K G Seshadri wrote a paper on ‘the endocrinology of love’. It remains among the most cited works on the subject in India. He says there are two components involved in attraction and love: the hormonal, driven by evolutionary instincts, and the development of companionship regulated by the brain’s reward system.
“Love involves three motivations,” says the endocrinologist. “Lust, fuelled by testosterone and oestrogen, seeks sexual union; attraction helps select genetically suitable partners, conserving time and energy in mating; attachment sustains long-term affiliate connections, ensuring stability and bonding in relationships. Trust sustains relationships, hormones drive attraction.”
Genetics also plays a role, says Dr Seshadri, who is planning another paper on the subject. “Some animals, such as prairie voles, are genetically wired for pair bonding. Humans share this tendency.
Our ancestors saw fidelity as key to survival, and studies too show monogamous societies thrive. Pair bonding is imprinted in our biology, reinforced by neuroendocrine pathways.” But as society changes, so does the idea of love, he says.
“Early exposure to sexual content and normalisation of infidelity are shaping modern relationships. Epigenetics may play a role in passing down traditional values that keep families together.”
In 2024, philosopher Pärttyli Rinne, a visiting researcher at Aalto University’s Brain and Mind Laboratory, published a study in the journal ‘Cerebral Cortex’ on types of love, the focus of his research for 15 years.
Using functional magnetic resonance imaging, which tracks brain activity by measuring blood flow, his team studied 55 participants in long-term relationships, all of whom had at least one child. In an interview with TOI, Pärttyli said romantic love activates the medial superior and middle frontal gyri, temporal regions, insula, amygdala, hippocampus and cerebellum, all involved in processing emotions and forming memories. “Parental love involves similar areas but also activates the striatum (reward centre) and thalamus (emotional processing hub).”
He adds that love for pets showed less activation than love for humans. “Interestingly, pet owners’ love for their pets closely resembled interpersonal love.” Love for nature though activated brain regions such as the fusiform gyrus, linked to visual perception.
“Our study offers a new perspective on why attachment to close ones is stronger than to strangers, though brain mechanisms are similar,” says Pärttyli. His team is now exploring cross-cultural differences in experiences of love.
Brain regions and roles
Pituitary gland: Releases cortisol, causing stress and fluttering of heart
nucleus accumbens: Releases dopamine and plays role in motivation, reward and decision-making, also involved in addiction, ignites during courtship
Raphe nucleus: Releases serotonin, a mood regulator
Hypothalamus: Releases vasopressin and oxytocin, influences bonding and attachment and trust
Amygdala: Hypothalamus releases testosterone and oestrogen, but both affect amygdala, which is involved in processing emotions
Hippocampus: Activated in romantic love
Striatum: Lights up when people imagine parental love
Fusiform gyrus: engaged when there is love for nature
posterior cingulate cortex: Love for pets
Hopeless romantic or cautious lover?
The nucleus accumbens and insula (linked to empathy and emotions) interact with the prefrontal cortex (impulse control) and amygdala (emotion processing). Love decisions depend on which area is more active. Sometimes the all-engaging passion of romantic love suspends judgment, a critical prefrontal cortex function (meaning, fools rush in). If the amygdala dominates, a more careful, balanced approach prevails (you will tend to look before you leap).