Speaker 1: Why do briefly glimpsed people appear to be more attractive?
Speaker 1: Why did portrait photographers used to put vaciline on their
Speaker 1: lenses and what does that have to do with Instagram filters?
Speaker 1: Why are thirsty people more likely to perceive something as transparent?
Speaker 1: And what does any of this have to do with
Speaker 1: mating or optimal decision making or puberty or frogs or
Speaker 1: instincts or movie stars. Welcome to another episode of Inner
Speaker 1: Cosmos with me David Eagleman. I'm a neuroscientist and an
Speaker 1: author at Stanford and in these episodes, we sail deeply
Speaker 1: into our three pound universe to understand the relationship between
Speaker 1: our brains and our lives. Throughout this podcast, we're gonna
Speaker 1: try to gain a better understanding of ourselves by practicing
Speaker 1: the technique of viewing the familiar as strange. We'll look
Speaker 1: at instincts, things that we do naturally, so naturally that
Speaker 1: we never even think to question them. But digging in
Speaker 1: on these things is how we come to develop a
Speaker 1: deeper understanding of ourselves. And today's episode is about the
Speaker 1: absolutely fascinating topic about how our brains determine for us
Speaker 1: what we find beautiful. So beauty is found all around us,
Speaker 1: in nature and in art and in music, and a
Speaker 1: good life is full of beautiful moments like a sunset
Speaker 1: or a compliment or a child's smile. But our interest
Speaker 1: today is in people, and specifically on the notion of attraction,
Speaker 1: So the notion of the movie star whose next movie
Speaker 1: you just can't wait to see, mostly because you find
Speaker 1: that person just so magnetically good looking, or the work
Speaker 1: made or the neighbor or the person you knew from
Speaker 1: your childhood who's just so amazingly attractive. So what is
Speaker 1: going on in the brain here, What are the signals
Speaker 1: that tell you that person is attractive? And what does
Speaker 1: all that have to do with the propagation of the species.
Speaker 1: So let's get started. There are hundreds of ways that
Speaker 1: a person can be attractive to you, based on their
Speaker 1: with or their brawn, or their kindness or their dedication
Speaker 1: to a cause or whatever. But what we're going to
Speaker 1: zoom in on today is about the first glimpse of someone,
Speaker 1: the rapid assessment that takes your breath away, and that
Speaker 1: magic moment is actually the end result of a great
Speaker 1: deal of computation that your brain is doing under the hood. Now,
Speaker 1: to start off, there's plenty of variation in what any
Speaker 1: given person finds beautiful, and there's some amount of variation
Speaker 1: across cultures too, in terms of how people dress and
Speaker 1: how they act, and their bone structure and their facial
Speaker 1: structure and all that. But what's interesting is that attractiveness
Speaker 1: is not all in the eye of the beholder, and
Speaker 1: beyond the personal and the cultural variations, some of the
Speaker 1: most salient elements of attractiveness are hardwired. When researchers study attractiveness,
Speaker 1: even cross culturally, they find a surprising concurrence in what
Speaker 1: gets rated highly. There are particular things that draw us,
Speaker 1: and mostly this has to do with largely unconscious signals
Speaker 1: of health and fertility. And in a sense, you already
Speaker 1: know this. Just look at the massive popularity of Instagram
Speaker 1: and TikTok filters, which are used around the world. These
Speaker 1: beautification filters aren't random. Instead, they move things in a
Speaker 1: particular direction such that the photos look better to us,
Speaker 1: and they work so much so that many young people
Speaker 1: are totally unwilling to post photos without these filters in place.
Speaker 1: So why what are these about? Let's look at this
Speaker 1: from the point of view of biology. When you open
Speaker 1: a biology textbook or watch a David Attenborough special, you
Speaker 1: see bower birds or lions, or frogs, or butterflies or fish,
Speaker 1: and you see these elaborate mating rituals. And of course,
Speaker 1: being members of the animal kingdom, we can't pretend that
Speaker 1: we don't have neural circuitry devoted to the same thing
Speaker 1: as well, because one of the most important drives for
Speaker 1: all creatures, including humans, is mate selection. How an animal
Speaker 1: chooses who to reproduce with. And we see this all
Speaker 1: across the animal kingdom, with feathers, with colors, with pheromones,
Speaker 1: with behavioral displays, all all creatures are trying to do
Speaker 1: things to make themselves more attractive to mate with. Now
Speaker 1: the question is how does this play out in humans.
Speaker 1: Needless to say, the reason you exist is because every
Speaker 1: single one of your ancestors successfully mate it. That's the
Speaker 1: single reason that you are here. Our species is so
Speaker 1: successful at reproduction that we've taken over the entire planet
Speaker 1: and the whole history of our species. Reproduction is driven
Speaker 1: by attraction, judgments and issues of mate choice. Now, the
Speaker 1: very first thing that blows my mind is how these
Speaker 1: algorithms for finding something attractive get programmed into the genes,
Speaker 1: which unfold the wiring of the brain and allow us
Speaker 1: to grow up and have this attraction and sexual drive.
Speaker 1: Because the weird thing is we inherit this psychological drive
Speaker 1: for sexual interaction, but it doesn't kick in for years.
Speaker 1: Is like thirteen years. So somehow the psychological machine code
Speaker 1: is pre programmed genetically, but it gets archived for years
Speaker 1: and years. So let's think about that. Everything that we
Speaker 1: study in biology happens on the scale of milliseconds. You've
Speaker 1: heard me talk about electrical spikes and neurons these last
Speaker 1: one millisecond, and gene expression and chemical reactions and cells
Speaker 1: and the CREB cycle and so on. All these things
Speaker 1: are trucking along at the nanosecond time scale. So the
Speaker 1: idea of programming something out of this material that takes
Speaker 1: thirteen years to unpack is mind blowing. Now, how do
Speaker 1: we know that sexuality isn't something that's learned? Well, Sometimes
Speaker 1: young children get damage to their brains, usually via an
Speaker 1: infection that leads to encephalitis, and then they end up
Speaker 1: doing things that look like sexual acts, even though they're
Speaker 1: too young to understand what they're doing. They end up
Speaker 1: expressing these programs too early. And that's how we know
Speaker 1: that these programs are in there, just waiting to be unpacked.
Speaker 1: So for everyone else, for whom this program unpacks at
Speaker 1: the right time. Once we've hit puberty, suddenly kids find
Speaker 1: themselves paying attention to body parts that they never paid
Speaker 1: much attention to before. If you draw a curvy line
Speaker 1: and show it to a seven year old boy and
Speaker 1: ask him to describe what he sees, he'll describe it
Speaker 1: as mountains or an ocean wave or something. But show
Speaker 1: him this exact same curved line when he's thirteen, and
Speaker 1: he can't help but interpret the line as breasts and
Speaker 1: buttocks and so on. Nothing changed in the outside world,
Speaker 1: but his brain changed on the inside such that the
Speaker 1: interpretation of the world changes. So we are hardwired. We're
Speaker 1: preprogrammed to, at the right time be attracted to others,
Speaker 1: like frogs to smell or by, or flies to colors,
Speaker 1: or bower birds to a good nest and so on,
Speaker 1: And suddenly it sucks up a lot of our mental energy.
Speaker 1: And I'm stating the obvious here. This is because there
Speaker 1: are few pressures as important as the evolutionary pressure to mate. Now,
Speaker 1: something that's wild about this pre programming is that it
Speaker 1: is very species specific. You don't find a horse's lips
Speaker 1: kissable or a monkey's eyes something that you want to
Speaker 1: gaze into romantically. But from a biologist's point of view,
Speaker 1: they're not that different. They accomplish the same function using
Speaker 1: the same machinery running on the same biological program. So
Speaker 1: what's the difference. The difference is that you are pre
Speaker 1: programmed to be mesmerized by the equipment of your own species,
Speaker 1: and not by the wrong keys to a different lock,
Speaker 1: even though they're so similar biologically. Now, note that to
Speaker 1: the frog or the monkey or the turkey vulture, their
Speaker 1: mate is the most magnetic thing in their world. You
Speaker 1: could stand all day naked in front of a frog
Speaker 1: and it just wouldn't care at all. It would have
Speaker 1: zero interest in you. But if you stick the right
Speaker 1: frog in front of it, that's the most wonderful, magnetic,
Speaker 1: dizzying thing in the world, and they'll expend great effort
Speaker 1: to get over there. So this notion of attractiveness drives everything,
Speaker 1: But you typically don't have conscious access to the details
Speaker 1: running under the hood. I mentioned in an earlier episode
Speaker 1: about the unconscious brain. An experiment in which men were
Speaker 1: asked to rank the attractiveness of different women's faces and photographs.
Speaker 1: So the men flipped through all these photographs and ranked
Speaker 1: each one from one to ten. Unbeknownst to the men,
Speaker 1: in half the photos the women's eyes were dilated, but
Speaker 1: in the other half they weren't, and the men were
Speaker 1: consistently more attracted to the women with di dilated eyes.
Speaker 1: But the men didn't have any insight into their decision making.
Speaker 1: None of them said, oh, I noticed that her pupils
Speaker 1: were two millimeters larger in this photo than this other one. Instead,
Speaker 1: they simply felt more drawn towards some women than others,
Speaker 1: for reasons they couldn't put a finger on. In the
Speaker 1: largely inaccessible workings of their brains, something new that a
Speaker 1: woman's dilated eyes correlates with sexual excitement. Their brains knew this,
Speaker 1: but the men did not, not explicitly. They also presumably
Speaker 1: didn't know that their feelings of attraction are deeply hardwired,
Speaker 1: steered in the right direction by programs carved over millions
Speaker 1: of years of natural selection. So when the men were
Speaker 1: picking up their pencil and making their choices, they didn't
Speaker 1: know that the choice was not theirs. Really, but instead
Speaker 1: the choice of successful programs that had been burned deep
Speaker 1: into the brain's circuitry over the course of hundreds of
Speaker 1: thousands of generations. The great psychologist William James was one
Speaker 1: of the first to really point to the hidden nature
Speaker 1: of instincts, and he suggested that we coax instincts into
Speaker 1: the light by a simple mental exercise. Try to make
Speaker 1: the natural theme strange by asking the why of any
Speaker 1: instinctive human act. So I'm going to read you an
Speaker 1: incredible passage that he wrote in eighteen ninety, and it
Speaker 1: goes like this quote, Why do we smile when pleased
Speaker 1: and not scowl? Why are we unable to talk to
Speaker 1: a crowd as we talk to a single friend. Why
Speaker 1: does a particular maiden turn our wits so upside down?
Speaker 1: The common man can only say, of course we smile.
Speaker 1: Of course our heart palpitates at the sight of a crowd.
Speaker 1: Of course we love the maiden, that beautiful soul clad
Speaker 1: in the perfect form, so palpably and flagrantly made for
Speaker 1: all eternity to be loved. And so probably does each
Speaker 1: animal feel about the particular things it tends to do
Speaker 1: in the presence of particular objects. To the lion. It
Speaker 1: is the lioness which is made to be loved to
Speaker 1: the bear, the she bear to the bruty. Hen the
Speaker 1: notion would probably seem monstrous that there would be a
Speaker 1: creature in the world to whom a nest full of
Speaker 1: eggs was not the utterly fascinating and precious, and never
Speaker 1: to be too much sad upon object which it is
Speaker 1: to her. Thus we may be sure that, however mysterious
Speaker 1: some animal's instincts may appear to us, our instincts will
Speaker 1: appear no less mysterious to them end quote. So our
Speaker 1: most hardwired instincts have usually been left out of the
Speaker 1: spotlight of inquiry because we don't think to ask them,
Speaker 1: and because psychologists have spent a lot of time working
Speaker 1: to understand uniquely human acts like higher cognition, or how
Speaker 1: things go wrong like human mental disorders. But the most automatic,
Speaker 1: effortless acts, those that require the most specialized in complex
Speaker 1: neural circuitry, they've been in front of us all along,
Speaker 1: and in the case of today's exploration, that's the notion
Speaker 1: of sexual attraction. Now, before I get back to that,
Speaker 1: I want to make a general neuroscience point. The more
Speaker 1: obvious and effortless something seems, the more we need to
Speaker 1: suspect that it seems that way only because of the
Speaker 1: massive circuitry that's living behind it. Take something like seeing,
Speaker 1: the active seeing is so easy and rapid precisely because
Speaker 1: we have so much circuitry dedicated to it. About a
Speaker 1: third of the brain is devoted to vision. The more
Speaker 1: effortless something seems, the more we can be pretty sure
Speaker 1: that there's a lot of cycles being burned under the
Speaker 1: hood to make it appear so. And the same principle
Speaker 1: applies to our sexual attractions. Our lust circuits are not
Speaker 1: driven by the shiny faced frog because we cannot mate
Speaker 1: with frogs and they have nothing to do with our
Speaker 1: genetic future. On the other hand, we do care quite
Speaker 1: a bit about subtle human body language, or the dilation
Speaker 1: of eyes or the fleshing of skin, because those things
Speaker 1: broadcast important information about something that could impact our genetic future.
Speaker 1: We live inside the fish bowl of our instincts, and
Speaker 1: we typically have as little perception of them as the
Speaker 1: fish does of its water. So our sense of beauty
Speaker 1: and attraction is burned deeply and inaccessibly into the brain,
Speaker 1: all with the purpose of accomplishing something biologically useful. So
Speaker 1: think about the most beautiful person you know, just magnetic,
Speaker 1: just some shouldn't say kuhah. When that person walks into
Speaker 1: the room. The geography of the room changes a bit
Speaker 1: as everyone turns to look. Our brains are exquisitely honed
Speaker 1: to pick up on those signals. Simply because of small
Speaker 1: details of symmetry and structure, that person enjoys a destiny
Speaker 1: of greater popularity and faster promotions and a more successful career.
Speaker 1: Our sense of attraction is not something just to be
Speaker 1: studied by the pens of poets, but instead, our sense
Speaker 1: of beauty results from specific signals that plug into dedicated
Speaker 1: neural software the key in the lock. So I'll share
Speaker 1: with you some data, and this is all research that
Speaker 1: scientists have performed in the laboratory and published peer reviewed
Speaker 1: papers on. I will say that there seems to be
Speaker 1: more literature on what males attractive. But keep in mind
Speaker 1: that even though it's often said that males are more
Speaker 1: visually driven, much of this research goes the other way too.
Speaker 1: And if you hear this data and you think, well, wait,
Speaker 1: what about our gay friends, keep in mind that the
Speaker 1: drive of attraction is deeply built into our psychology, and
Speaker 1: sometimes the gender someone is attracted to can switch, but
Speaker 1: the fundamental drives in the brain remain the same. This
Speaker 1: is because the drive to reproduce is really the most
Speaker 1: ancient brain circuitry we have, So even if someone does
Speaker 1: not reproduce personally, they're still equipped with and driven by
Speaker 1: the same circuitry which drives them towards sex. So let's
Speaker 1: return to what I said at the beginning, which is
Speaker 1: that the signals driving us are generally correlated with signals
Speaker 1: of health and fertility. So until puberty, the faces and
Speaker 1: body shapes of boys and girls are essentially similar. But
Speaker 1: the rise in estrogen in pubescent girls gives them fuller lifts,
Speaker 1: while testosterone and boys produces a more prominent chin and
Speaker 1: a larger nose and a fuller jaw. Estrogen causes the
Speaker 1: growth of breasts and buttocks, while testosterone encourages the growth
Speaker 1: of muscles and broad shoulders. So for a female, full lips,
Speaker 1: full buttocks, narrow waste. This broadcasts a clear message I'm
Speaker 1: full of estrogen and fertile. For a male, it's the
Speaker 1: full jaw, the stubble, the broad chest. This is the
Speaker 1: kind of stuff that we're programmed to find beautiful. The
Speaker 1: external signs tell us something about the internal, and our
Speaker 1: neural programs are so ingrained that there's not much variation
Speaker 1: across the population. Researchers have measured a surprisingly narrow range
Speaker 1: of the female proportions that males find most attractive. The
Speaker 1: optimal ratio between the waist and hips is typically between
Speaker 1: point sixty seven and point eight. Back when Playboy centerfolds
Speaker 1: were a thing, researchers studied those and found that their
Speaker 1: waist hip ratios remained at about point seven over time,
Speaker 1: even over the decades as the average weight of a
Speaker 1: centerfold moved up or down. As women grow older, their
Speaker 1: features change in ways that depart from these proportions, their
Speaker 1: middles sticking, their lips thin, their breasts sag, and so on,
Speaker 1: all of which broadcasts the visual signal that they are
Speaker 1: past peak fertility. So a young man ends up being
Speaker 1: less attracted to an elderly woman than to a young
Speaker 1: adult woman. His neural circuits have a clear mission reproduce,
Speaker 1: and his conscious mind receives only the need to know headline,
Speaker 1: she's really attractive, and nothing more. All these computations are
Speaker 1: performed unconsciously. Now, males are often more visually driven than females,
Speaker 1: but women are nonetheless subject to the same internal forces.
Speaker 1: They are drawn by the attractive features that flag the
Speaker 1: maturity of manhood. Now, an interesting twist is that a
Speaker 1: woman's preferences can change depending on the time of month.
Speaker 1: Women prefer masculine looking men when they're ovulating, but when
Speaker 1: they're not ovulating, the data suggests that they prefer softer features,
Speaker 1: which presumably flag more social and caring behavior. Although the
Speaker 1: programs of seduction and pursuit run almost entirely unconsciously, the
Speaker 1: endgame is obvious to everyone, and this is why millions
Speaker 1: of people shell out billions of dollars for facelifts and
Speaker 1: tummy tucks and implants and light bosuction and botox. They're
Speaker 1: working to tap into that strong correlation in other people's
Speaker 1: brains between their external and internal. They're working to maintain
Speaker 1: the keys that unlock the pro programs in other people's brains. So,
Speaker 1: as I've said, we have almost no direct access into
Speaker 1: the mechanics of our attractions. Instead, visual information plugs into
Speaker 1: ancient neural modules that drive our behavior. Recall that experiment
Speaker 1: that I just mentioned when men ranked the beauty of
Speaker 1: women's faces. They found the women with dilated eyes more
Speaker 1: attractive because dilated eyes signal sexual interest, but the men
Speaker 1: had no conscious access to their decision making process. Now
Speaker 1: I'll give you another piece of data which is sort
Speaker 1: of mind blowing and demonstrates how deeply and unconsciously we
Speaker 1: pick up on signals. First, consider this strange fact that
Speaker 1: human females are unique among primates and that they participate
Speaker 1: in mating year round. They don't broadcast any special signal
Speaker 1: to publicize when they are fertile, and this is totally
Speaker 1: different from other primates who have these periodic cycles of
Speaker 1: being in heat. All other female mammals give off clear
Speaker 1: signals when they're in heat. For example, in female babboons,
Speaker 1: the rear end turns bright pink, which is an unmistakable
Speaker 1: and irresistible invitation for a male baboon. Human females just
Speaker 1: don't give off signals like this, or don't they. It
Speaker 1: turns out that a woman is considered to be most
Speaker 1: beautiful just at the peak of fertility in her menstrual cycle,
Speaker 1: about ten days before mensi's. This is true whether she
Speaker 1: is judged by men or by women, and it's not
Speaker 1: a matter of how she acts. It's perceived this way,
Speaker 1: even if people are just looking at her photograph, so
Speaker 1: her good looks broadcast her level of fertility. Her signals
Speaker 1: are more subtle than the baboons, but they only need
Speaker 1: to be clear enough to tickle the dedicated, unconscious machinery
Speaker 1: of the males in the room. If the signals can
Speaker 1: reach those circuits, the mission is accomplished. The signals also
Speaker 1: reach the circuitry of other females. Women are quite sensitive
Speaker 1: to the effect of other women's cycles, perhaps because this
Speaker 1: lets them assess their competitors when competing for mates. It's
Speaker 1: not yet clear what the tip offs for fertility are.
Speaker 1: They may include some qualities of the skin, or the
Speaker 1: fact that a women's ears and breasts become more symmetrical
Speaker 1: in the days leading up to ovulation. Whatever the constellation
Speaker 1: of clues are, our brains are engineered to latch on.
Speaker 1: Even while the conscious mind has no axis. Your mind
Speaker 1: simply senses the almighty and inexplicable tug of desire. The
Speaker 1: effects of ovulation and beauty are not not just assessed
Speaker 1: in the laboratory. They are measurable in real life situations.
Speaker 1: Some years ago I'm not making this up. There was
Speaker 1: a study by scientists who counted up the tips made
Speaker 1: by exotic dancers at the local strip clubs and correlated
Speaker 1: this with the menstrual cycles of the dancers. And what
Speaker 1: they found is that during peak fertility, dancers raked in
Speaker 1: an average of sixty eight dollars an hour. When they
Speaker 1: were menstruating, they earned only about thirty five dollars, and
Speaker 1: in between they averaged about fifty two dollars. So although
Speaker 1: these women were presumably acting flirtatiously throughout the month, their
Speaker 1: change in fertility was broadcast to hopeful customers by changes
Speaker 1: in body odor, skin, wasted, hip ratio, and possibly their
Speaker 1: own confidence as well. Now, interestingly, dancers on birth control
Speaker 1: didn't show any clear peak in performance and earned only
Speaker 1: a monthly average of thirty seven dollars per hour versus
Speaker 1: an average of fifty three dollars per hour for dancers
Speaker 1: not on birth control. Presumably they earned less because the
Speaker 1: pill leads to hormonal changes and cues indicative of early pregnancy,
Speaker 1: and so the dancers were presumably slightly less magnetic to
Speaker 1: the customers in the club. All this research drives home
Speaker 1: the point that the pulls we feel are built deeply
Speaker 1: into our neural machinery. We don't have conscious access to
Speaker 1: the programs and can only surface these issues with careful studies.
Speaker 1: And the part that's always amazed me is how subtle
Speaker 1: these signals are. The brain is picking up on these
Speaker 1: really small signals. So think again about that really attractive
Speaker 1: person you know, and imagine that you measured the distance
Speaker 1: between his or her eyes and nose length and lip
Speaker 1: thickness and chin shape and so on. If you compare
Speaker 1: those measurements to those of a a not so attractive
Speaker 1: person you know, you would find that the differences are
Speaker 1: really subtle, like a centimeter here, a centimeter there, But
Speaker 1: it makes a big difference in your final judgment. So
Speaker 1: imagine you took these two people, one attractive, one not
Speaker 1: so attractive, and showed them to a space alien. That
Speaker 1: two humans would look indistinguishable to the alien in the
Speaker 1: same way that attractive and unattractive space aliens would be
Speaker 1: difficult for you to tell apart, But the small differences
Speaker 1: within your own species, these have a great deal of
Speaker 1: effect in your brain. As an example of tiny differences,
Speaker 1: just consider that some people might find the site of
Speaker 1: a woman in short shorts intoxicating, and a male in
Speaker 1: short shorts less attractive. Even though the two scenes are
Speaker 1: hardly different. From a geometrical perspective, male and female legs
Speaker 1: just don't look that different. Both are built on the
Speaker 1: same architecture. They're both hinged limbs made of femurs and
Speaker 1: knee caps and skin and so on, and the differences
Speaker 1: between them are swamped by the similarities. I mean, if
Speaker 1: I showed you a female hawk and a male hawk,
Speaker 1: you really couldn't tell the difference between them. But other
Speaker 1: hawks are exquisitely sensitive to these differences. With all these animals,
Speaker 1: they're so similar that you really have to train up
Speaker 1: to see the differences. And this is the point I
Speaker 1: want to make. We are so exquisitely tuned to the
Speaker 1: differences in humans, and we don't even realize it. Our
Speaker 1: ability to make subtle distinctions is exquisitely fine grained. Our
Speaker 1: brains are engineered to accomplish the clear cut task of
Speaker 1: mate selection. In pursuit, all of the computation lives under
Speaker 1: the surface of conscious awareness. We get to simply enjoy
Speaker 1: the lovely feelings that bubble up. And I'll give you
Speaker 1: another example of this attractive misjudgments are not only constructed
Speaker 1: by your visual system, but they're influenced as well by smell.
Speaker 1: So odor carries a great deal of information, including information
Speaker 1: about a potential mate's age, sex, fertility, identity, emotions, health.
Speaker 1: The information is carried by a flotilla of drifting molecules,
Speaker 1: so in many animal species, these compounds drive behavior almost entirely.
Speaker 1: In humans, the information often flies beneath the radar of
Speaker 1: conscious perception, but they nonetheless influence our behavior a bit.
Speaker 1: So imagine we give a female mouse a selection of
Speaker 1: males to mate with. Her choice is not random. Instead,
Speaker 1: it's based on the interplay between her genetics and the
Speaker 1: genetics of her suitors. But how in the world would
Speaker 1: she have access to that kind of hidden information about genetics.
Speaker 1: While all mammals have a set of genes known as
Speaker 1: the major histocompatibility complex or MHI, these genes are key
Speaker 1: players in our immune systems, So given a choice, the
Speaker 1: mouse will choose a mate with dissimilar MHC genes. Because
Speaker 1: mixing up the gene pool is almost always a good
Speaker 1: idea in biology. It keeps genetic defects to a minimum
Speaker 1: and leads to a healthy interplay of genes known as
Speaker 1: hybrid vigor, So finding genetically distant partners is useful, But
Speaker 1: how do mice who are largely blind pull this off
Speaker 1: with their noses? An oregon inside their noses picks up
Speaker 1: on pheromones, which are floating chemicals that carry signals through
Speaker 1: the air, signals about things like alarm or food trails,
Speaker 1: or sexual readiness, or in this case, genetic similarity or difference.
Speaker 1: Now do human sense and respond to pheromones the way
Speaker 1: mice do? This is an area of debate in the
Speaker 1: signe literature, but recent work has found receptors in the
Speaker 1: lining of the human nose just like those used in
Speaker 1: pheromonal signaling and mice. It's not clear if our receptors
Speaker 1: are functional, but the behavioral research is suggestive. So in
Speaker 1: a study at the University of bern researchers measured and
Speaker 1: quantified the MHCs of a group of male and female students.
Speaker 1: The males were then given cotton T shirts to wear
Speaker 1: so that their daily sweat soaked into the fabric, and
Speaker 1: then later back in the laboratory, females plunged their noses
Speaker 1: into the armpits of these T shirts and picked which
Speaker 1: body odor they preferred. The result was exactly like the
Speaker 1: mice they preferred the males with more dissimilar MHCs. So
Speaker 1: apparently our noses also influenced our choices, again flying the
Speaker 1: reproduction mission under the radar of consciousness. And I'll just
Speaker 1: note that beyond reproduction, human pheromones may also carry invisible
Speaker 1: signals in other situations. For example, newborns preferentially move toward
Speaker 1: pads that have been rubbed on their mother's breast rather
Speaker 1: than clean pads, presumably based on pheromonal cues, and the
Speaker 1: length of women's menstrual cycles may change after they sniff
Speaker 1: the armpit sweat of another woman. So again, although pheromones
Speaker 1: clearly carry signals, the degree to which they influence human
Speaker 1: behavior is unknown. Our cognition is so multilayered that these
Speaker 1: cues have been reduced to bit players. Whatever other roles
Speaker 1: they have, pheromones serve to remind us that the brain
Speaker 1: is continuously evolving. These molecules unmask the presence of outdated
Speaker 1: legacy software. So all this led me to run some
Speaker 1: studies on attractiveness in my laboratory, And this puts us
Speaker 1: back to the question that I posed at the beginning,
Speaker 1: which is what is going on when you first look
Speaker 1: at a person and make some rapid judgment about their attractiveness.
Speaker 1: Human faces carry an enormous amount of information about emotional
Speaker 1: state and physical well being, and we are programmed to
Speaker 1: read faces like books. And in this light, it is
Speaker 1: not surprising that we rapidly form initial impressions about someone
Speaker 1: after a brief exposure. And one trait we extract unbelievably
Speaker 1: quickly is facial attractiveness. And you've probably noticed that sometimes
Speaker 1: a person passes by you for just a moment and
Speaker 1: your brain screams out that that person is highly attractive,
Speaker 1: and then you turn and you take a closer look
Speaker 1: and realize that your first judgment was actually wrong, and
Speaker 1: your attractiveness rating goes way down. So I started asking
Speaker 1: a number of people about this years ago and found
Speaker 1: that this was a common experience if you pay close
Speaker 1: to tension to your perception. So I started to wonder,
Speaker 1: is a briefly glimpsed person always more attractive, and if so,
Speaker 1: what is that about from an neural point of view,
Speaker 1: Because there's obviously less visual information that's harvested from a
Speaker 1: brief glimpse. So my student Don Vaughan, and I started
Speaker 1: researching this because here's the question. It is not at
Speaker 1: all clear why the brain would consistently AerR in one
Speaker 1: direction in its attractiveness judgments. In other words, why would
Speaker 1: a briefly glimpsed face tend to be interpreted as more
Speaker 1: attractive instead of less. After all, in most tasks of
Speaker 1: information processing, less information translates to less confidence and less value.
Speaker 1: You wouldn't pay more for a car that you knew
Speaker 1: less about. So we had fifty nine people participate in
Speaker 1: the study, half female, half male. Average age was twenty
Speaker 1: eight years old, and everyone rated photographs of either seventy
Speaker 1: five female seventy five mails. So you look at the
Speaker 1: computer screen and a photograph is flashed, and all you
Speaker 1: need to do is rate the photograph on a scale
Speaker 1: from one which is least attractive to ten most attractive,
Speaker 1: and then you see the next one in the next one,
Speaker 1: and you do this through all the photographs in random order.
Speaker 1: But here's the thing. First, you do this with twenty
Speaker 1: five photographs to just acquaint you with the rating scale
Speaker 1: and for us to gather your average ratings. You get
Speaker 1: to look at each photo for as long as you
Speaker 1: want no time pressure. Then in the second block, we
Speaker 1: use twenty five new photographs, and here you keep your
Speaker 1: eyes fixed on a red dot in the center of
Speaker 1: the screen, and after a random delay, a photograph gets
Speaker 1: flashed in the center of the screen for about a
Speaker 1: quarter of a second. Bang, real fast flash, and you
Speaker 1: register your attractiveness judgment. Then in the next block, you
Speaker 1: rate the same photographs, again presented in a random order,
Speaker 1: but this time with no time constraints. You can look
Speaker 1: for as long as you want. Then to recreate the
Speaker 1: effective catching a glimpse from the corner of your eye,
Speaker 1: we also ran a block where we presented photographs in
Speaker 1: your peripheral vision. So we use twenty five new photographs
Speaker 1: and it's the same as before, where you're keeping your
Speaker 1: eye on the red dot in the middle, but now
Speaker 1: we flash the photograph in a random position somewhere on
Speaker 1: the screen. Bang. What was that? By the time your
Speaker 1: eyes get there, it's gone, and then you register your
Speaker 1: attractiveness rating. Then in the final block, you rate those
Speaker 1: same twenty five photographs represented in the center in a
Speaker 1: random order with no time constraints. Okay, so what was
Speaker 1: the result? Briefly glimpsed photographs are rated as more beautiful
Speaker 1: everyone this, male and female rated attractiveness higher when they
Speaker 1: were just catching a glimpse, whether that was in the
Speaker 1: middle or on the periphery, so we summarized this result
Speaker 1: as the glimpse effect. For example, when a male saw
Speaker 1: a flash of a female in the periphery, he rated
Speaker 1: her on average almost a point higher than when he
Speaker 1: looked for as long as he wanted. And as a
Speaker 1: side note, although both females and males show the glimpse
Speaker 1: effect when judging photographs of either gender, the effect is
Speaker 1: most pronounced in males rating female photographs. And by the way,
Speaker 1: this is true no matter what your initial rating was,
Speaker 1: it goes down when you have a longer chance to look. So.
Speaker 1: In other words, if you catch a glimpse of someone
Speaker 1: rounding the corner or driving past quickly, your perceptual system
Speaker 1: will tell you that they are more attractive than you
Speaker 1: would otherwise judge them to be. Men show this effect
Speaker 1: more strongly, presumably because men are more visual in assessing attraction.
Speaker 1: When you catch a brief glimpse of someone, you believe
Speaker 1: you have just seen something amazing. Then when you go
Speaker 1: around the corner you find you were mistaken. So the
Speaker 1: glimpse effect is clear and measurable. But why does it happen.
Speaker 1: Why should the visual system, given just a bit of
Speaker 1: fleeting information, always err on the side of believing that
Speaker 1: someone is more attractive in the absence of clear data,
Speaker 1: Why wouldn't your visual system simply strike for the middle
Speaker 1: and judge the person to be average or even below average.
Speaker 1: So one way you explain these results is to think
Speaker 1: about what's called spatial frequencies. Something with high spatial frequency
Speaker 1: is changing a lot across space, while low spatial frequency
Speaker 1: doesn't change much. So think about it like if you
Speaker 1: had a lot of wrinkles, All those sharp lines provide
Speaker 1: a lot of high spatial frequency, but if your face
Speaker 1: is totally smooth, that's low spatial frequency. Anyhow, it's long
Speaker 1: been known that faces that come across as smoother are
Speaker 1: rated as more attractive. We don't really like the high
Speaker 1: spatial frequencies, the sharp lines and so on, and the
Speaker 1: visual system actually takes more time to process the fine lines,
Speaker 1: while the low frequency stuff is processed very rapidly. So
Speaker 1: when we flash of photograph really quickly, your visual system
Speaker 1: doesn't have access to the fine features that decrease ratings
Speaker 1: like skin blemishes, because your visual system is just processing
Speaker 1: the general shape of the smooth stuff going on. And
Speaker 1: this explains something about the way that portrait photography used
Speaker 1: to be done, especially in the earlier part of last century.
Speaker 1: How did photographers make people more attractive by putting vaciline
Speaker 1: on their camera lenses that created a soft focus effect
Speaker 1: that blurred the image to create what people regarded as
Speaker 1: a romantic look. But of course what they were doing
Speaker 1: was taking away information, taking away the sharp lines, in
Speaker 1: particular the high spatial frequencies, and just leaving the soft,
Speaker 1: dreamy stuff, which we find more attractive. Now we don't
Speaker 1: use vacline on lenses anymore, or don't we. That's exactly
Speaker 1: the trick with these Instagram filters. What these filters generally
Speaker 1: do is simply take away the high spatial frequencies. It's
Speaker 1: like the vaciline on the lens. No more little imperfections.
Speaker 1: Now you just have perfectly smooth skin for completeness. Soil
Speaker 1: also mention that these filters often do other things as well,
Speaker 1: like make lips bigger, because fertile women have full lips,
Speaker 1: but they don't when they're kids. Or elderly. Okay, so
Speaker 1: back to the big picture of the glimpse effect. We
Speaker 1: know that in a brief presentation you see less of
Speaker 1: the fine lines, and so maybe that's the explanation. But
Speaker 1: we also suggested there may be something to understand that's
Speaker 1: even a little bit deeper. So we proposed a second,
Speaker 1: non exclusive possibility, and this hypothesis pivots on the demands
Speaker 1: of reproduction. If you believe that a briefly glimpsed person
Speaker 1: is beautiful, and let's say they actually weren't, it only
Speaker 1: requires a double take on your part to correct the mistake.
Speaker 1: It's not much of a cost. But on the other hand,
Speaker 1: if you mistake an attractive mate for an unattractive one,
Speaker 1: you can say cyonara to your potentially rosy the genetic future.
Speaker 1: So it behooves your perceptual system to serve up a
Speaker 1: story that a briefly glimpsed person is attractive. So the
Speaker 1: idea is that the glimpse effect results from the combination
Speaker 1: of your sensory information with the utility of that information
Speaker 1: for the cognizanty. This is known as a Bayesian risk model.
Speaker 1: As an example of this sort of thing, imagine looking
Speaker 1: at a square of a certain color that's against squares
Speaker 1: of other colors, you might conclude that the square has
Speaker 1: a certain color, or you could equally conclude that the
Speaker 1: square is transparent and its color is being determined by
Speaker 1: the squares underneath it. So if you're asked, is this
Speaker 1: transparent or not, there's no single right answer. But it
Speaker 1: turns out what's found in the laboratory is that if
Speaker 1: you are thirsty, you are more likely to perceive it
Speaker 1: as transparent. Your visual system has a bi towards determining
Speaker 1: transparent things like water when you're thirsty. If you're not thirsty,
Speaker 1: you're not seeing water everywhere. Why it's because thirsty people
Speaker 1: have an increased utility for water. Finding water becomes more
Speaker 1: valuable to your brain, and if you accidentally see water
Speaker 1: when it's not there, what's called a false positive that
Speaker 1: doesn't matter so much. In other words, it behooves a
Speaker 1: thirsty brain to have a bias towards perceiving things that
Speaker 1: are water like. And this is the same idea here
Speaker 1: with the glimpse effect. Your brain doesn't want to miss
Speaker 1: its genetic future, so it has a bias towards seeing
Speaker 1: things as attractive. If you're interested in this topic. There's
Speaker 1: a field known as Bayesian decision making, and the idea
Speaker 1: is that your brain is not seeing maximum likelihood, as in,
Speaker 1: how likely is that driver next to me super attractive? Instead,
Speaker 1: it's aimed at maximizing expected utility. How useful is it
Speaker 1: for me to see things in this way? So in
Speaker 1: this framework, an ideal observer chooses the interpretation that's the
Speaker 1: most important rather than the most likely. So what we
Speaker 1: get is an increase in perceived attractiveness when you have
Speaker 1: limited information. And again, this is because the cost of
Speaker 1: an overestimate is cheap you just look a second time,
Speaker 1: but the cost of failing to identify an attractive potential
Speaker 1: mate is high. So what I told you about vacoline
Speaker 1: and Instagram filters is explainable just by getting rid of
Speaker 1: the high frequencies the sharp lines. But I think more generally,
Speaker 1: this issue of limited information is an important part of
Speaker 1: what's in play here because during the pandemic I talked
Speaker 1: with a lot of colleagues who work at the Stanford Hospitals,
Speaker 1: for example, and it turns out that the world ran
Speaker 1: a very interesting natural experiment from twenty twenty to twenty
Speaker 1: two in the form of wearing masks. The masks don't
Speaker 1: changeange anything about the high and low frequency information, but
Speaker 1: they take away all the information about one half of
Speaker 1: the face. And I heard from a lot of people,
Speaker 1: both male and female, that they sometimes met coworkers whose
Speaker 1: face they had never seen completely and stead they only
Speaker 1: ever saw the top half, and they felt that the
Speaker 1: person was really attractive. And at the end of the pandemic,
Speaker 1: when the masks finally came off and they finally saw
Speaker 1: the whole face, they were often a little disappointed. Now,
Speaker 1: was this because everyone had ugly mouths? No, it was
Speaker 1: because the brain of the viewer made assumptions about the
Speaker 1: half of the face that was not seen. I've informally
Speaker 1: quizzed dozens of people about this, and it wasn't that
Speaker 1: they assumed something in particular, something they could articulate about
Speaker 1: the other person's mouth. It's not like they were looking
Speaker 1: for a specific shape of the mouth. It's just that
Speaker 1: they assumed that it would be better. Again, when there's
Speaker 1: a lack of information, the brain it seems to make
Speaker 1: a judgment that's biased in the positive direction. It just
Speaker 1: assumes there's something better hiding behind the curtain. It's all
Speaker 1: about anticipation, and in an upcoming episode about prediction, I'm
Speaker 1: going to talk about why the most attractive person on
Speaker 1: a nude beach is the one who still has their
Speaker 1: clothes on. If you've ever been on a clothing optional beach,
Speaker 1: you'll know that everyone, men and women end up gazing
Speaker 1: towards the new person, the man or woman who's just arrived,
Speaker 1: because there's anticipation about what is going to be found there.
Speaker 1: There's a lack of information because they still have their
Speaker 1: clothes on, and so your brain assumes the best. But
Speaker 1: moments after that person disrobes, everyone's sort of over it.
Speaker 1: The internal positive assumptions have been replaced by reality. And
Speaker 1: we can see the same issue of this optimistic judging
Speaker 1: with the size of photographs. A lot of people find
Speaker 1: that when they're looking at some is Twitter profile or
Speaker 1: TikTok profile or LinkedIn photo, you think they look quite attractive,
Speaker 1: and then you click on the photo to make it bigger,
Speaker 1: and your assessment goes down. I've run some initial studies
Speaker 1: on this with small photographs and large photographs, and this
Speaker 1: is what we find. If a photo is small and
Speaker 1: you can't work out any details, you judge it as
Speaker 1: being higher in attractiveness. Now, this may again have to
Speaker 1: do with your inability to make out the small details
Speaker 1: in a small photo, but it also amounts to the
Speaker 1: same thing in space as the glimpse effect. In time.
Speaker 1: The lack of information leads to more dependence on your
Speaker 1: internal model, and our models tend to be hopeful. So
Speaker 1: let's wrap up. We know that across the biological kingdom
Speaker 1: there is a constant broadcasting of signals that most often
Speaker 1: we don't even have conscious access to. But as we
Speaker 1: dive deeper and deeper over the course of these episodes
Speaker 1: into all the computations happening under the hood that we
Speaker 1: don't have access to, we will see this vast empire
Speaker 1: of instincts that we've perhaps never even thought to question.
Speaker 1: We all find that it's obvious that we are more
Speaker 1: attracted to someone versus someone else. Of course, we're attracted
Speaker 1: who wouldn't be, And as William James pointed out, presumably
Speaker 1: every animal feels this way about the particular things that
Speaker 1: tends to do. As he said to the lion, it
Speaker 1: is the lioness which is made to be loved to
Speaker 1: the bear, the she bear, but the technique that allows
Speaker 1: us to really see ourselves is to be able to
Speaker 1: view the familiar as strange. With a little bit of work,
Speaker 1: we can step outside our internal models and see ourselves
Speaker 1: from a new angle. Today we talked about the instinct
Speaker 1: of attraction, and in future episodes we're going to see
Speaker 1: how deeply our instincts drive us in other domains, and
Speaker 1: how invisible these things are until we scratch the surface.
Speaker 1: Making the familiar strange is perhaps the only way to
Speaker 1: really come to understand ourselves and to illuminate the enigmas
Speaker 1: inside our three pound inner cosmos. To find out more
Speaker 1: and to share your thoughts, head over to eagleman dot
Speaker 1: com slash podcast. Send me an email at podcast at
Speaker 1: eagleman dot com with questions or discussion, and I'll be
Speaker 1: making an episode soon in which I address those. Until
Speaker 1: next time, I'm David Eagleman, and this is Inner Cosmos.