In "The Big Bang Theory," the second time Raj met Claire, his mind already conjured images of their future together: in a cozy little house, he sat on the sofa vividly recounting "How I Met Your Mother" to their grown-up children, while Claire cradled a newborn baby.
The first time I met someone, I was already planning our wedding – while not everyone is like this, such elaborate fantasies are not uncommon when we encounter a crush.
It's a mechanism that activates in the brain's prefrontal cortex when love strikes.
It's "romantic love" – a uniquely human phenomenon at the conscious level, differentiating us from other mammals.
On July 3rd, British entrepreneur Steven Bartlett interviewed Anna Machin on his YouTube channel "The Diary Of A CEO."
Anna Machin is an evolutionary anthropologist currently working at the Department of Experimental Psychology at Oxford University.
If you want to understand modern love from the perspective of the brain, hormones, humanities, and psychology, then check out this compiled interview.
Raj and Claire
As Helen Fisher said, these apps shouldn't be called "dating apps"; at most, they are "introduction apps."
Steven Bartlett:
I have a friend who's been single for a long time, and one day he asked me, "Steve, what am I doing wrong?"
To be honest, I don't have much experience, nor am I qualified to judge others' rights and wrongs. But he showed me his dating app profile and said, "Look, I rejected this person."
I took a look and thought, "My God, they're so good-looking!" Like someone straight out of a movie. And from the chat history, there was nothing unusual.
Then my friend clicked on another photo and said, "But look, there are several cardboard boxes on her wardrobe."
It's inexplicable but true: people will rule each other out based on very superficial details, calling them "red flags."
My friend deduced from various "clues" that his potential date was living with their parents, "either just moved in, or about to move out, so they haven't settled down yet."
Anna Machin:
Similar to "red flags" is "ick," a new social media term for something that instantly turns you off.
The problem with online dating is that you can't use all your senses to judge this living, breathing person, unlike in a face-to-face encounter.
So people just stare at those few photos, frantically analyzing every corner of the image. Honestly, whether someone has cardboard boxes on their wardrobe has nothing to do with your compatibility. As Helen Fisher said, these apps shouldn't be called "dating apps"; at most, they are "introduction apps," giving you the chance to meet more people, nothing more.
Helen Fisher, American anthropologist.
May 31, 1945 – August 17, 2024
You're not really dating someone on an app, and you can't truly understand who they are. You're just getting to know one more person. So, once you have the chance to meet offline, that's when your brain should be allowed to work its magic – it's been evolving for half a million years.
Steven Bartlett:
Everything you've said resonates with my friend's situation. And, as far as I know, some people can add 100 friends and still be single. Logically, there should be someone suitable among 100 people, right?
What exactly is going on?
Anna Machin:
I think there are two main points. Firstly, the barrier to entry for dating apps is very low. In the past, when we dated, it usually started with meeting someone offline, either at a bar, at work, or through friends – which was essentially a blind date. You had to think about what to wear, where to go, and spend money, then go on the date and spend some time with the person at a cafe or restaurant.
These were real investments. But now, you can open a dating app anytime, anywhere – on the subway, while cooking, or watching Netflix, you can just swipe.
Steven Bartlett:
I saw a study, though the scenario was a bit different, but the gist was: the more you invest in something, the more likely you are to value it.
Anna Machin:
Exactly right.
Steven Bartlett:
This study gathered some people and had them browse a mediocre forum with no entry requirements, then asked them for their opinions on it. The answer was, "It's boring."
Then they found another group of people, and this time, people had to go through a series of verifications to enter the same forum. When asked, "What do you think of this forum?" most people said, "It's great. I really like it."
I recall the entire preparation process for my first date at 14: I didn't have much money then, and asking someone to the movies was a big deal. I thought about what to wear for 3 days. At the cinema, I was nervous the whole time. I felt like I was falling in love with the person, just because of all the effort I put in.
Anna Machin:
Exactly.
Another point is the "paradox of choice." When there are too many options, we find it harder to make a decision. On dating apps, this paradox is even more apparent. Especially if you're good-looking, you'll have matches like a buffet – you can just keep swiping and swiping.
Steven Bartlett:
It's similar to my experience at a Thai restaurant. The menu was like a directory, and the waiter said, "We can make anything." Then I sat there agonizing for about... 45 minutes.
Anna Machin:
So, you see, our brains are simply not designed for such situations. From this perspective, dating apps actually disable your brain because they provide so little information, simply not enough to activate your brain's complex and powerful "mate selection algorithm."
More and more people are realizing that "romantic love" is not the only form of "love."
Steven Bartlett:
A few weeks ago, I was chatting with another friend.
We talked about our lives and current goals, and I asked him, "Do you want to get married? Do you want kids?" He said, "No interest at all. What I want is financial freedom, to buy a house, and I currently have about 150 plants, and I want to get over 200."
Sounds a bit incredible, right? But, I'm actually hearing similar answers more and more often. Marriage and having children are no longer life's prerequisites but have become "personal choices."
Anna Machin:
Indeed, we are living in an era where "personal desires are increasingly respected." Instead of family/clan/societal expectations, we are more concerned with: is this the life I truly want to live?
Another important point is that more and more people are realizing that "romantic love" is not the only form of "love." Sometimes, the most crucial relationships that support us emotionally and practically may not be romantic partners, but friends, our chosen "psychological family" (not limited to our birth family, anyone who can provide us with emotional security).
So, some people no longer prioritize romantic love or parent-child relationships as their primary life goals.
In a sense, this is a good thing – it means that various forms of love are placed on equal footing, and I can love in these ways, which in itself is beautiful.
But does this mean we are moving away from that "holding hands until old age" type of long-term companionship? As someone once asked me, "Is marriage disappearing?"
My answer is: No.
We will always use some ritualistic way to mark the existence of a romantic relationship – regardless of your gender or sexual orientation, this need will always exist.
Steven Bartlett:
Before you came, I looked up some data, let me read it:
• In England and Wales, nearly 40% of adults have never been married, reaching a historical high.
• Only 38% of single women are actively seeking partners, while for single men, this figure is 61%.
• Morgan Stanley predicts that by 2030, 45% of women aged 25 to 44 will be single.
The last one is also what interests me most:
• Approximately 70% of divorces are initiated by women, indicating that women are more willing to actively leave when facing an unsatisfactory marriage.
My question is, what are your thoughts on this? And, have people's "views on love" changed in today's society?
Anna Machin:
In the past, women had to get married, and having children out of wedlock was unacceptable. Marriage was not only a social norm but also your economic security. Many marriages had nothing to do with love; they were simply pragmatic choices.
But now, women have been liberated from that framework. This also appears in older women, especially post-menopause.
A hundred years ago, women were lucky to live to 50 (roughly the average age of menopause), but now, the upper limit of human lifespan is constantly being refreshed. For women, this period of life after menopause can be as short as 20 years or as long as 50 years.
So, some of them will re-examine their lives. A clear trend verifies this: divorces initiated by women over 50 are significantly increasing.
They look back at their partners and think, "I chose you then because that's the life I wanted – I wanted children, a warm family."
"But now I look at you and ask myself: Are you the one I want to spend the next stage of my life with?"
Aunt Su Min, prototype for the film "The Will to Leave"
Steven Bartlett:
Why is that?
I'm asking this purely for selfish reasons – I don't want my partner to dump me when she's 50...
Anna Machin:
Let me think where to start...
Human "love" is special because it involves two completely different areas of the brain.
First, there's your limbic system, which is the emotional center and our "unconscious brain region." Evolutionarily speaking, this area is very ancient, having existed for millions of years.
And "attraction" – the initial flutter – originates here.
We call it the first stage of romantic love, based on primal biological instincts, and thus a "love" mechanism shared by us and other mammals.
You know, that moment when your eyes meet across a crowded room. You receive a vast amount of sensory information at that instant.
Visually, from appearance, body shape, to gait, and whether they look healthy. If you are female, you will also subtly sniff – this is because women can smell genetic compatibility, even though the act is completely unconscious.
Steven Bartlett:
Wait, so – men can't smell that?
Anna Machin:
You can also smell scents, but it's just scent; you can't smell if you two are genetically compatible.
This has to do with something called MHC, which stands for major histocompatibility complex.
Steven Bartlett:
Wow, what's that?
Anna Machin:
It's the foundation of the human immune system, a very complex set of genes. What's amazing is that this set of genes also determines your sense of smell – your ability to smell things.
For women, they can perceive the similarity of a male's MHC genes to their own through scent: too similar carries the risk of inbreeding. Conversely, the greater the difference, the stronger the future baby's immune system will be, with the underlying logic being a more diverse genetic combination.
So you "smell" this person, but this process is completely unconscious. And your brain's limbic system – the part that governs emotions and intuition – automatically receives this "olfactory result."
Steven Bartlett:
How do we know this? Have there been experiments?
Anna Machin:
There are several ways to verify it.
The most famous is the "T-shirt experiment": a group of men wear very ordinary white T-shirts for 24 hours. During this time, they cannot shower, spray perfume, or use any deodorizing products.
Then, these T-shirts are individually sealed in bags, and then we ask some unsuspecting women to – uh, I apologize – smell them one by one.
Their task is to identify the one they find "most appealing" or "most attractive." The hypothesis is that the scent chosen by each participant represents the male behind it with the greatest genetic difference from her.
The results proved the hypothesis to be true – genetic typing showed significant differences between the pairs.
And now, this test is very mature; there's a company in Switzerland where you just spit and send it in, and they can tell you how much difference there is in your and your partner's MHC.
Steven Bartlett:
I'm wondering why men haven't evolved this ability...
Anna Machin:
Our speculation is that if a woman makes a mistake and gives birth to a genetically too similar baby, the cost is much greater than for a man.
Think about it: pregnancy plus caring for a child means that for over 9 months, she temporarily loses the opportunity to procreate with other potential partners, while men do not.
From an evolutionary perspective, regardless of gender, our brains quietly do one thing: assess the "Biological Market Value" of the person in front of us. For example, can this person produce healthy offspring? Driven by biological instinct, we choose the person best suited for reproduction with ourselves, thereby transmitting our genes in the most optimal way.
And the source of information is sensory: the other person's appearance, voice, and scent.
Just as men look at the waist-to-hip ratio, women unconsciously "scan" the person in front of them.
Steven Bartlett:
If women rely on scent for mate selection, what do men rely on?
Anna Machin:
Waist-to-hip ratio.
The experiment goes like this: participants wear eye-tracking devices and walk casually on the street. Without knowing the true purpose of the experiment, their first gaze point is the most natural. The results show that most people's first scan is not the face, but the waist-to-hip ratio.
Cross-cultural studies also found that the most attractive waist-to-hip ratio is 0.7, also known as the "hourglass figure."
Steven Bartlett:
Cross-cultural means...?
Anna Machin:
We showed photos with different waist-to-hip ratios to men from different countries and cultural backgrounds, and almost all of them pointed to the same ratio, 0.7, as the most attractive.
Moreover, it has nothing to do with weight. Some cultures prefer fuller figures, some prefer thinness, but either way, the key is the ratio between the waist and hips.
This is because this ratio is directly related to fertility. Women with this waist-to-hip ratio typically have higher estrogen levels, and furthermore, it indicates that she is far from menopause – after entering menopause, women's body shape begins to masculinize, and the ratio approaches 1 (waist and hips are about the same width), which is due to decreased estrogen and increased testosterone.
We also found that women with a waist-to-hip ratio of 0.7 have a lower risk of certain chronic diseases, including diabetes, heart disease, and even some types of cancer.
So what you're actually assessing is how healthy this woman is and what her fertility potential is.
In other words, if I decide to enter a relationship and temporarily stop looking for other partners, will I ultimately be able to have offspring? And is she healthy enough to raise a child?
Steven Bartlett:
So, what do women look at in eye-tracking experiments?
Anna Machin:
Women look at the shoulder-to-waist ratio: broad shoulders, narrow waist, also known as an "inverted triangle" body shape.
The ideal shoulder-to-waist ratio is 1.6. But don't rush to measure your waist, because – only Olympic-level athletes reach 1.6. And, I have to say: for women, visuals are really not the most important thing.
Steven Bartlett:
1.6, so if my waist is 100, my shoulders have to be 160?
Anna Machin:
That's right.
Just as men look at the waist-to-hip ratio, women unconsciously "scan" the person in front of them.
That said, this ratio is quite interesting. It shows that women are indeed attracted to certain male traits. Firstly, an inverted triangle intuitively means no fat accumulation around the abdomen – for men, this is an important health indicator.
Secondly, people with this body type are often strong and appear very protective. Furthermore, it conveys information: this person has excellent testosterone levels, and testosterone has been confirmed to be positively correlated with self-confidence and competitiveness.
What a great deal of research tells us is that in a long-term relationship, one of the most valued traits is kindness.
Steven Bartlett:
I want to know, when we encounter a crush, what exactly is happening with that series of wonderful chemical reactions in our bodies?
Anna Machin:
We often say, "falling in love."
In that moment of "falling," it's actually the brain's nucleus accumbens that is activated. We can observe it being highly active in brain imaging; at this time, large amounts of dopamine and oxytocin flood in, and both are essentially "love hormones," especially oxytocin, which makes a person more willing to open up.
You must know that the amygdala is the source of emotions like anxiety and fear. Imagine seeing your crush in a restaurant, and you're agonizing over whether to go over and say hello. But what if they ignore you? How awkward would that be?
Such self-doubt scenarios are precisely manifestations of an overactive amygdala. So, what oxytocin does is: calm your amygdala. This way, you can relax and regain confidence.
But oxytocin alone isn't enough; you'd be too relaxed to move at all.
That's when dopamine comes in. It's like a motivational hormone, pushing you forward – "No, you have to go over there and talk to them!"
So, you walk through the crowd towards your crush, and you start talking... And when the other person starts speaking, your brain's neocortex, especially your prefrontal cortex, begins to light up.
Here in the prefrontal cortex, there's a "mentalizing & empathizing area." And empathy is the foundation of a relationship, and even of love itself.
Steven Bartlett:
What does mentalizing mean?
Anna Machin:
In simple terms, it's mind-reading. In other words, can you understand the other person's emotions and intentions? This is not only crucial for the conversation to unfold but also helps you identify whether the other person is lying.
It's a bit unfortunate that this area tends to "shut down" a bit in the early stages of a relationship.
Ultimately, what makes human love unique is the connection between our "rational judgment system" (prefrontal cortex) and our "subconscious reward system" (striatum). They can work in concert.
We've all felt that flutter and the wonderful chemical reactions. However, once the other person starts speaking, your consciousness and rationality begin to intervene. This is key to differentiating our mate selection mechanism from other mammals, and it's the second stage of romantic love.
Imagine, during a conversation, the other person says something that makes you very uncomfortable, or they're harsh, humorless, etc. At this point, the rational part of your brain will jump out and say, "No, no, no, this person won't do." It directly overturns that previous "biological instinct attraction."
Steven Bartlett:
What are some things that most easily make someone lose interest on the spot?
Anna Machin:
The worst is unkindness.
What a great deal of research tells us is that in a long-term relationship, one of the most valued traits is kindness. So, if you say something harsh, especially directed at others present, or if you belittle something important to the other person when you don't yet know them well, that's truly a "turn-off."
Steven Bartlett:
The example that comes to mind is disrespect towards service staff.
Anna Machin:
Exactly.
People who act imperiously towards service staff really infuriate me. Because in that moment, you see the most core aspect of that person.
The key to whether a relationship can last is not height or hobbies, but personality, values, and belief systems.
So, for example, if someone suddenly says something seriously homophobic or racist, I'll immediately think, "OK, bye, this person can't go on with me."