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