Abstract core knowledge may shape the basins of cultural attraction: romantic kissing as a case study
– by Hossein Samani & Ashley J. Thomas
It may be easy for many readers to assume that romantic kissing (lip-to-lip contact between romantic partners) is universal. While romantic kissing is common around the world, it is far from universal. On the other hand, rather than spreading from a single point of origin, ethnographic and historical evidence suggests that kissing has been ‘invented’ independently at different times and places. This combination—widespread but not universal, and seemingly reinvented multiple times—is what we set out to explain. Our central claim is that romantic kissing is best understood as a cultural invention that reappears because it aligns with how humans intuitively understand intimacy. We argue that similarities in how everyone understands intimacy create a sort of gravitational pull, or “basin of attraction,” that makes some ways of signaling intimacy (like kissing) much more intuitive, and therefore more likely, than others.
To make sense of a cultural practice like romantic kissing, we broke down the question into two parts: (1) What problem does this practice solve? (2) Why does it take this particular form? Consider writing. Writing systems around the world differ in countless ways, but they all solve similar problems: they let us record and transmit information across time and space. The features of writing systems are shaped by the limits of our minds and bodies. Though diverse, writing systems around the world tend to be composed of relatively simple, easy-to-distinguish shapes that are easy to produce. We can ask the same questions about kissing. What is it for? And why lip-to-lip contact rather than the endless other actions that could signal romance? Our answer is that romantic kissing is particularly intuitive to all humans as a way to communicate and intensify intimate bonds, and it serves to convey a special kind of intimate bond, i.e., romantic love, where and when romantic love is important.
We start with the idea of “cultural attractors.” This idea, from theories of cultural evolution, argues that cultural evolution is affected by the structure of the human mind. Practices that resonate with existing biases, cognitive tools, or innate representations are easier to invent, imitate, and remember. While this process does not determine practices, over time, cultures tend to converge on practices that are easier for people to reproduce and understand. Crucially, this process doesn’t determine exact behaviors. It doesn’t include the specific practice of kissing. Instead, it shapes the landscape so that some practices that are more intuitive to understand and easy or more pleasurable to reproduce create ‘gravitational pulls’. Romantic kissing, we argue, is one such practice.
To understand why, we incorporate the idea of ‘core knowledge’ which explains how humans—starting in infancy—make sense of the world, including social relationships. Over the past several decades, research on infants has challenged the idea that babies begin life with only sensory impressions and gradually build toward abstract concepts. Instead, there is now strong evidence that infants come equipped with what’s called core knowledge: domain-specific systems that represent abstract aspects of the world—objects, agents, numbers, space. It enables infants to make sense of situations or entities the first time they encounter them and to learn quickly about their specific environment. Recent evidence suggests these ideas can be extended to social relationships. Importantly, even infants seem to distinguish between friendly and socially intimate relationships. Specifically, they link physical closeness, such as using the same spoon, to emotional closeness, such as comforting someone. In these studies, infants predicted that a woman who shared a single orange slice with a puppet by eating some herself, putting it in the puppet’s mouth, and then back in her mouth, would be the one to comfort the puppet when it was sad. We argue that because very young infants recognize this, it is likely universal, and this is why romantic kissing is intuitive.
Next, we asked about the purpose of romantic kissing. Romantic love itself seems to appear in many cultures, but its importance and distinctiveness vary. In some places and historical periods, romantic love is central to marriage, identity, and life decisions. In others, it’s less salient than, say, loyalty to kin or community, or it’s not strongly separated from other forms of affection. In societies where romantic love is not as sharply defined or highly valued, the specific need that kissing solves is less present. Other practices—such as different forms of affection, ritual, or sex—may carry the load instead. Conversely, as societies change—economically, demographically, ideologically—and romantic love becomes more salient, we would expect to see increases in both how much people talk about romantic love and how central romantic kissing becomes as a symbol of it. Our proposal is that romantic kissing becomes common and symbolically powerful in cultures where romantic love is treated as a distinct and important relationship category and where people need a clear, intuitive way to express and signal that specific bond.
Given that humans share intuitions about intimacy, lip-to-lip kissing—with very close bodily contact, synchrony, and the exchange of saliva—fits those needs extremely well. We argue that people could easily learn that kissing is a way to communicate that “this relationship is special.” Kissing itself also likely triggers intense feelings of being moved or deeply connected, which further reinforces its role. In that sense, romantic kissing functions as a cultural technology: it leverages universal intuitions to address a local social problem—how to signal, deepen, and display romantic love.
It is also possible that romantic kissing is costly. Kissing is not just intimate; it’s risky. It involves the face and mouth, carrying a risk of injury (from biting) and pathogen transmission through saliva sharing. From a signaling perspective, that’s exactly what you might want in a commitment device: something you wouldn’t do with just anyone. From an evolutionary perspective, romantic love can be a high-stakes relationship because it involves commitment to a single person. Costly signals may help distinguish genuine commitment from casual interaction.
In the end, we don’t think romantic kissing is “in our genes” in any simple sense. Nor do we think it’s a mere historical accident. Instead, we see it as a recurring cultural solution built on universal knowledge of what it means to be close to someone. By studying infants, cross-cultural data, and historical change together, we can begin to see why certain practices—like kissing—are common but not universal.
