Attraction is driven by a combination of brain chemistry, sensory cues, psychological patterns, and social context. No single factor determines who you find attractive. Instead, your brain runs a rapid, mostly unconscious evaluation that weighs physical signals, emotional states, familiarity, and even your own hormone levels at that moment. Here’s what science has identified as the key forces at work.
Your Brain’s Reward System Fires First
The earliest spark of attraction is largely a neurochemical event. When you encounter someone you find attractive, a region deep in your brain’s reward system lights up, the same area associated with pleasure, focused attention, and the motivation to pursue rewards. Brain imaging studies using photographs of romantic partners consistently show activation in this reward center, confirming that attraction hijacks the same circuitry involved in other forms of desire and motivation.
Three chemicals do most of the heavy lifting in early attraction. Dopamine drives the feeling of wanting, the pull toward someone that makes you think about them constantly and seek them out. Norepinephrine produces the physical symptoms you associate with a new crush: alertness, racing heart, sweaty palms, loss of appetite, and that feeling of being unable to sleep. It also sharpens your memory for new experiences, which is why early encounters with someone you’re attracted to feel so vivid. Meanwhile, serotonin activity shifts in ways that resemble obsessive thinking patterns, which helps explain the intrusive, can’t-stop-thinking-about-them quality of new attraction.
Oxytocin enters the picture as attraction deepens. It reduces anxiety and promotes feelings of security and trust, essentially calming the stress response that early attraction triggers. This creates an interesting arc: the initial phase of attraction is genuinely stressful, driven by cortisol and norepinephrine, and the resolution of that stress through bonding and closeness is part of what makes the progression from infatuation to attachment feel so rewarding.
Physical Cues Signal Health and Fertility
Certain physical traits are consistently rated as attractive across cultures, and most of them track with markers of health and reproductive fitness. Facial symmetry is one of the most studied. Symmetrical faces are generally rated as more attractive, likely because developmental symmetry signals a robust immune system and low exposure to environmental stressors during growth.
Body proportions matter too. For women’s bodies, men most frequently prefer a waist-to-hip ratio around 0.65 to 0.75, with the average preferred value landing near 0.7. This isn’t arbitrary. Low-to-average waist-to-hip ratios in women are associated with better cardiovascular health, higher fertility, fewer anovulatory cycles, and even higher cognitive ability. Values above 0.75 or below 0.65 are preferred less often. The alignment between what men find attractive and what predicts good health supports the idea that these preferences evolved as a way to identify healthy mates, though there’s considerable individual variation in what any given person prefers.
Hormones Shift What You Find Attractive
Your hormonal state actively recalibrates your preferences. Women with higher estrogen levels show stronger attraction to men with higher testosterone, and this preference fluctuates across the menstrual cycle. Near ovulation, when fertility peaks, women express stronger attraction to masculine facial features, deeper voices, and other testosterone-linked traits. During other phases of the cycle, these preferences weaken.
This means attraction isn’t a fixed calculation. The same face can register as more or less appealing depending on where you are in a hormonal cycle, suggesting that the brain continuously adjusts its mate-evaluation criteria based on current reproductive status. Similar hormone-driven preference shifts have been documented across many species, but the human version is subtler and layered with social and cultural influences.
Scent Plays a Role, but Not the Way You Think
Popular culture loves the idea of human pheromones, invisible chemical signals that trigger irresistible attraction. The reality is more complicated. Most mammals detect pheromones through a specialized structure called the vomeronasal organ. In humans, this organ develops in the embryo but then regresses. Adults may still have visible vomeronasal cavities, but they lack the sensory neurons, nerve fibers, and brain structures needed to process pheromone signals. The genes that code for vomeronasal receptors are mutated and nonfunctional in humans.
That said, body odor does influence attraction through your regular sense of smell. Early research in mice suggested that animals prefer mates with different immune system genes (called MHC genes), detected through scent, because offspring with more diverse immune genes would be better at fighting off a wider range of pathogens. This idea was extended to humans through the famous “sweaty T-shirt” studies. However, a meta-analysis of 23 studies found no significant correlation between immune gene similarity and scent preferences in humans. The effect, if it exists at all, is far weaker than the mouse studies suggested. You may well prefer certain people’s natural scent over others, but the mechanism behind that preference remains unclear.
Proximity and Familiarity Build Attraction
One of the most reliable predictors of attraction is simple physical closeness. The proximity effect describes a positive correlation between how near you are to someone and how likely you are to develop an attraction to them. This works partly through exposure: being close to someone increases how often you encounter them, which creates more opportunities for interaction, which builds familiarity. And familiarity, in general, breeds liking. This is why so many relationships form among coworkers, classmates, and neighbors.
There’s an important caveat, though. Proximity amplifies whatever reaction you’re already having. If your early impressions of someone are negative, increased exposure can intensify dislike just as easily as it intensifies attraction. Proximity doesn’t create attraction from nothing. It accelerates tendencies that are already forming.
Knowing Someone Likes You Changes Everything
One of the most powerful and underappreciated drivers of attraction is simply learning that someone is interested in you. This reciprocity of liking effect is considered one of the most reliable findings in social psychology, demonstrated across age groups, between individuals and groups, and in a wide range of social contexts. When you discover that someone finds you attractive or likable, your own feelings toward them shift upward, often substantially.
This effect has evolutionary roots. For ancestral humans, knowing that another person viewed you favorably was valuable social information. It signaled safety, potential cooperation, and mating opportunity. Your brain is essentially wired to reward you for paying attention to people who pay attention to you.
Your Body Can Trick You Into Attraction
In a now-classic 1974 experiment, 85 men were approached by an attractive female interviewer either on a high, swaying suspension bridge or on a low, stable bridge. The men on the fear-inducing bridge wrote stories with significantly more sexual content and were far more likely to call the interviewer afterward. When a male interviewer ran the same protocol, no differences appeared between the two bridges.
This demonstrated what psychologists call misattribution of arousal. Your body produces similar physical responses to fear and attraction: elevated heart rate, shallow breathing, heightened alertness. When you’re already physiologically aroused by something unrelated, like exercise, a scary movie, or a rickety bridge, your brain can misinterpret that arousal as attraction to whoever happens to be nearby. This is why first dates involving exciting or mildly nerve-wracking activities tend to generate stronger feelings of chemistry than dinner-and-a-movie.
Similarity Matters Less Than You’d Expect
The idea that “opposites attract” is a cultural staple, but so is the competing idea that people are drawn to those who are similar to them. Research over the past several decades has tried to settle this debate, and the answer is somewhat surprising: neither effect is as strong as people assume.
An eight-year longitudinal study using sophisticated statistical methods found that personality similarity explained a small or negligible amount of variance in relationship well-being compared to other factors. The one consistent finding was that similarity in agreeableness (how cooperative and warm both partners are) predicted women’s experience of feeling supported. Beyond that, what mattered far more than being alike was each partner’s individual personality traits. In the researchers’ words, most of the personality-relationship “action” is driven by who each person is individually, not by how closely matched the pair is.
This doesn’t mean shared interests and values are irrelevant to attraction. They clearly help people connect in the early stages by giving them something to talk about and common ground to build on. But the deep-seated belief that finding your personality “match” is the key to lasting attraction isn’t well supported by the data. A kind, emotionally stable partner tends to make for a satisfying relationship regardless of whether their personality mirrors yours.