Tinder and Bumble would be a lot more effective if you could sniff your potential matches before swiping. Better yet, if you could smell them and hear them. Forget complex matching algorithms—just invent a way to spritz the person's scent while you listen to them talk or read aloud (pro tip: go for “May I Feel Said He” by e.e. cummings, especially if you sound like Tom Hiddleston).
You're not just attracted to someone for their brains or their brawn, or even just for their perfectly symmetrical face. Those things are all part of the equation that also includes that person's scent and voice. We've known for decades that attraction—and not just sexual attraction, mind you—has many components that fit together, yet it's a relatively under-studied area. Physical beauty's role has historically been far more central to the study of attraction. Symmetrical faces, specific chest-to-waist or hip-to-waist ratios, height—they've all been consistently tied to attractiveness. How smells and speech factor in has been studied a lot less, and the research that's out there has gotten less attention.
So a group of psychologists got together to examine three decades' worth of research on what olfactory and vocal cues bring to the equation. They published their review in Frontiers in Psychology on Thursday. Going on smell alone, both sexes can tell when their partner is healthy and if they're genetically and immunologically compatible, according to studies on the subject. Men tend to prioritize physical attractiveness more than women, who tend to prefer scent. Women can tell when a man is more dominant and when he's more attractive based on his natural odor, while men can tell when a woman is fertile. A person's voice gives similar cues, with the addition of traits like cooperativeness and physical strength. In case it wasn't obvious already, most of this research is heterosexual by nature. Sexual attraction studies nearly all focus on male-female pairings, and if they do test female-female or male-male attraction it's generally as a comparison point, not a part of the main research. So take everything else in this article with a great big heaping of heteronormative salt.
All of these results might sound pretty primitive. Maybe you'd even call them animalistic. And there is a key player here that we haven't mentioned: the vomeronasal organ. You might know it better as the part of the body that reacts to hormones called pheromones. Lots of animals, from reptiles to mammals to insects, rely on these molecules to send signals like sexual attraction, aggression, fear, territory, and pathways. It's also what some animals use to test a female's pee to see if she's ovulating. So there's that.
When we talk about sexual attraction in humans, it's tempting to talk about pheromones and our animal instincts. The trouble is that humans probably aren't influenced by pheromones at all.
Biologists still aren't even sure whether or not humans have a functioning vomeronasal organ to detect pheromones in the first place. We may have some remnant of it, but it seems to have been cut off from the rest of the body. There doesn't appear to be any physical connection between the organ and the rest of the central nervous system, and the genes related to its function have all become pseudogenes—related but no longer functional versions of real genes.
Vomeronasal organs aside, there are a few theories for why attraction is so multimodal for humans. One is that the combination of factors simply gives you the best estimation of your compatibility. On its own, a man's chest-to-waist ratio isn't a good predictor for sexual health and attraction, but combine it with the tone of his voice, his scent, and his height and suddenly you have a much better picture. A second, related idea is that each individual trait isn't all that predictive of compatibility, but since there's no evolutionary reason to eliminate the weak preference for said traits they stick around—like vestigial organs, but sexier. We aren't sure what kind of messages our bodies are broadcasting or picking up on through these cues, let alone how our interpretation of them changes if, for example, we aren't able to use all five senses, or we aren't participants in a male-female meet cute. As is so often the case, more research is needed.