38 minute read
Our World
HOW OUR SENSES WORK
Our nerves relay signals to the brain, which interprets them as sight (vision), sound (hearing), smell (olfaction), taste (gustation) and touch (tactile perception). These five basic human senses help us perceive and understand the world around us.
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Chemicals in the air stimulate signals that the brain interprets as smells. Equipped with 400 olfactory receptors, humans may be able to detect more than 1 trillion scents, according to the National Institutes of Health. We can accomplish this impressive feat thanks to the olfactory cleft found on the roof of the nasal cavity next to the region of the brain responsible for interpreting smell — the olfactory bulb and fossa. When we sniff or inhale through the nose, chemicals in the air bind to specialized nerve receptors located on hairlike cilia at the top of the nasal cavity. This triggers a signal that travels up a nerve fiber to the olfactory bulbs then along the cranial nerves and down the olfactory nerves toward the olfactory area of the cerebral cortex, enabling the brain to interpret what we are smelling.
Olfactory bulb Olfactory tract Cribform plate Olfactory nerves
Nasal cavity
Hearing
The complex labyrinth that is the human ear uses bones and fluid to transform sound waves in the air into electrical signals. Music, laughter, speech — all reach our ears as sound waves in the air. The outer ear funnels the waves down the narrow passageway called the ear canal to the eardrum, or tympanic membrane, creating mechanical vibrations. The eardrum transfers the vibrations to the middle ear, occupied by the auditory ossicles. These three tiny bones — the malleus (hammer), incus (anvil) and stapes (stirrup) — amplify and transport the vibrations, sending them to the cochlea, a snail-shaped structure filled with fluid in the inner ear. There, tiny specialized hair cells detect pressure waves in the fluid, activating nervous receptors that send electrical signals through the auditory nerve toward the brain, which interprets the signals as sounds.
Ossicular chain
Auditory nerve
Auditory canal
Eardrum Cochlea Epidermis
Meissner corpuscle
Pacinian corpuscle
Hypodermis Merkel cell
Touch
Specialized receptors within our skin relay tactile sensations to our brain via peripheral nerves. Thought to be the first sense that humans develop, touch consists of several distinct sensations communicated to the brain through specialized neurons in the skin. Our skin is made up of three major layers of tissue: the outer epidermis, middle dermis and inner hypodermis. Within these layers, specialized receptor cells detect tactile sensations and relay signals through peripheral nerves toward the brain. The presence and location of the different types of receptors make certain body parts more sensitive. Merkel cells and Meissner corpuscles both detect touch, pressure and vibration. Other touch receptors include Pacinian corpuscles, which also register pressure and vibration, and the free endings of specialized nerves that feel pain, itching and tickling.
Circumvallate papillae
Taste bud
Cornea
Pupil
Iris Lens Fungiform papillae
Optic nerve
Retina Sclera
Taste
Taste buds on the tongue enable us to identify what we are eating. The small bumps, or papillae, on the surface of the tongue contain taste buds. The number of taste buds we have can vary widely; the average person has between 2,000 and 8,000, which are replaced every two weeks or so. Most are located on the tongue, but they also line the back of the throat, the epiglottis, the nasal cavity and the esophagus. Chemicals from food stimulate gustatory cells inside the taste buds, activating nervous receptors which send messages to the brain — in particular to the thalamus and cerebral cortex — enabling us to identify whether the food we are eating tastes sweet, sour, bitter, salty or savory.
Sight
Our eyes translate light into image signals for the brain to process. The dome-shaped cornea is transparent to allow light to enter the eye and curved to direct it through the pupil, which is an opening in the iris (the colored part of the eye). The iris works like the shutter of a camera, dilating or constricting to control how much light passes through the pupil and onto the lens. The curved lens then focuses the image onto the retina. This light-sensitive layer of tissue at the back of the eye is a delicate membrane of nervous tissue containing photoreceptor cells. These cells, shaped like rods and cones, translate light into electrical signals. Cones translate light into colors, central vision and details. Rods translate light into peripheral vision and motion and enable vision in limited light. These signals travel from the retina through the optic nerve to the occipital lobe near the back of the brain. There, the visual cortex interprets them to form visual images.
A Question of Taste
From sautéed grasshoppers to fusion food, USC Dornsife scholars use taste as a passport to explore diverse cultures, histories and identities.
By Susan Bell
Sporting miniature chef’s hats and blindfolds, my 4-yearold son and a dozen other under-fives at his Paris public preschool gathered excitedly around a long table covered with a cheerful red-and-white checked tablecloth. They were observing “La Semaine du Goût,” an annual week-long celebration of that most French of senses: taste. Set before them were different foods representing the five basic tastes: sweet, sour, salty, bitter and savory. The game was to sample each — without peeking — and correctly identify its taste.
This national awakening of the senses through the education of the palette is a perfect example of the importance French culture places on taste. Nor is it a one-off exercise. This emphasis on the cultivation of taste continues throughout a French child’s education. Each weekday, 7 million public school children receive a four-course, subsidized lunch that would be the envy of most adults worldwide.
Each meal features a different cheese course with a typical starter of artichoke hearts, lentil or beet salad. Main courses might include roast chicken with green beans or salmon lasagna with organic spinach while dessert is typically a healthy serving of fresh fruit. The foods many Americans associate with classic kids’ fare — pizza, hamburgers and fish sticks — are served in French schools once a month at most. Thus, an entire nation grows up with an appreciation for healthy food and a palette trained to enjoy a wide variety of sophisticated flavors.
A PASSPORT TO DIVERSITY More than 5,000 miles away in Los Angeles, USC Dornsife is taking the concept of taste as a teaching tool considerably further. Michael Petitti, associate professor (teaching) of writing in the Thematic Option program, is one of several USC Dornsife scholars who use taste as a passport to explore multiple cultures — all without leaving L.A.
His Maymester course “From Pueblo to Postmates” is inspired by the work of the late Jonathan Gold, the Pulitzer Prize-winning food writer renowned for his culinary explorations of the L.A. area and the historical unpacking through food of its past and the myriad diasporas that call it home.
The course provides insights into L.A.’s ethnic and cultural diversity, how that’s expressed through taste, and how the city intersects and comes together through its culinary creativity.
TAKEAWAYS “You can map the history of L.A. through food,” says Petitti. “We spend a lot of time in Boyle Heights, now a predominantly Latino area but which, like much of East L.A. during the early to mid-20th century, used to be a Jewish neighborhood with numerous Kosher restaurants and food stores.”
Petitti broadens his students’ palettes by taking them to “El Mercadito de Los Angeles,” a Latino market where they taste “nopales” salsa with cactus and “chicharron” burrito — crispy, crunchy pork rinds cooked in a fiery chili sauce made with cactus and wrapped in a tortilla. They also try dried salsa garnished with pumpkin seeds and chili flakes and sample a new fusion of Lebanese and Mexican cuisine that serves up falafel made with chorizo.
In the San Gabriel Valley — a Japanese and Mexican enclave for much of the early to mid-20th century and now inhabited by a Chinese immigrant diaspora — Petitti takes his students to eat authentic dim sum.
In South L.A., students explore the prolific Mexican American and Latino food scene, eating fresh tamales and visiting a working farm in Compton — a city that was once L.A.’s agrarian heart.
Guest speakers, such as Los Angeles Times columnist Gustavo Arellano, also provide expert insider views on the evolution of different areas of L.A.
“One of the most rewarding aspects of this class is that many native Angelenos have taken it and say it opened their eyes to the city, its history, neighborhoods, cuisine, and how others live and experience it. Students discover new insights into the complexity and richness of L.A. through our readings, visits, and guest speakers, as well as their ethnographic interviews and final research projects. That nuanced, epiphanic experience of L.A. is the goal of the course,” Petitti says.
A RICH STEW Another USC Dornsife scholar using taste as a lens to understand the city’s complexities is Sarah Portnoy, professor (teaching) of Spanish, who has been teaching Latino food culture for 12 years. Her courses put students in touch with their senses while increasing their Spanish vocabulary and widening their knowledge and experience of Latino culture.
Portnoy agrees with Gold’s description of L.A. as “a rich mosaic.”
“The wealth of Mexican cuisine here is unparalleled in the United States,” she says. “We have the largest population of Koreans anywhere outside of Seoul. We have Salvadorean, Guatemalan, Pakistani, Filipino and Japanese communities — among many others.”
This rich stew of overlapping cultures has provided the perfect springboard for the creation of fusion food, led by pioneers like Roy Choi, founder of the legendary Kogi food trucks, renowned for their Korean Mexican combos.
To sample the vast array of flavors found in the city’s Latino communities, Portnoy takes her students to visit restaurants and to meet chefs and street vendors.
She encourages students to establish a sense of place and history as she prompts them to describe the tastes they encounter.
“I ask them to find out the story behind the restaurant and then to describe the neighborhood, what the place looks like and the diners, before talking about the dish, the colors, the key ingredients, the aromas and what they evoke. Then I ask them to find a metaphor for their experience,” she says.
Portnoy extends this learning experience to her threeweek Maymester course in Oaxaca, Mexico. There, she invites students to taste and describe such unfamiliar items as crunchy “chicatanas” (ants), smoky mezcal and spicy salsas made from a variety of local chilies.
FOOD, IDENTITY AND PLACE Portnoy’s scholarship focuses on food-centered life histories. Her work was rewarded this year with a more than half million-dollar grant from the National Endowment for the Humanities, shared with her teaching partner, to make a documentary series that explores culture and cuisine on both sides of the Mexico border. Abuelitas (Grandmothers) on the Borderland will be filmed in L.A. and three other U.S. cities, as well as the grandmothers’ Mexican towns of origin. Her partner in the project is Amara Aguilar, professor of journalism at the USC Annenberg School for Communication and Journalism
Earlier in 2022, Portnoy curated the museum exhibition “Abuelita’s Kitchen: Mexican Food Stories,” which showcased the role traditional dishes played in the lives of 10 Mexican and Mexican American grandmothers living in L.A. and how they passed their culinary knowledge on to their children and grandchildren.
Comprising oral histories, kitchen artifacts and recipes, the exhibition also featured a documentary produced by Portnoy and filmed by USC Dornsife alumni about the grandmothers’ relationships with food, identity and place.
“Food-centered life histories have the capacity to portray the voices and perspectives of women who have traditionally been ignored or marginalized,” says Portnoy. “This project aims to amplify the voices of a group of indigenous, “mestiza” (of mixed indegenous and Spanish descent), Mexican American and Afro Mexican grandmothers who have cooked, preserved, and passed on Mexican food culture, while creating communities and cultures that are unique to Southern California.”
THE TASTE OF LOVE Portnoy says the project aims to capture not only traditional recipes, but how food is woven through the fabric of the women’s lives. Many of their stories are deeply moving, such as that of Maria Elena who recounts spending long hours selling tamales from a cart in Watts in South L.A. so she could feed her five young children.
Another abuelita, Merced, is filmed preparing “mole poblano” from her Mexican home state of Pueblo. Merced has not been able to return to Mexico to see her children and parents for more than 20 years, but she says the taste of this thick, savory chocolate and chili sauce connects her to them — and particularly to her mother.
“Merced can no longer touch her mother,” Portnoy says, “but still feels viscerally connected to her by this dish she taught her to make as a child.”
The documentary delivers an emotional punch: Food connects generations through tastes, recipes and traditions, but most importantly it is an act of love.
“I asked each of the abuelitas ‘What does this dish represent to you?’” Portnoy says. “They all responded, ‘Amor’ (love).”
TASTING THE PAST So, taste can connect us to our family, our history and our homeland. But it can also serve as a passport that enables us to travel through time.
A prime example is Petitti’s favorite L.A. restaurant, The Musso and Frank Grill. Dripping in history, the legendary dining room was the storied haunt of literary heavyweights William Faulkner, Ernest Hemingway, Dorothy Parker and F. Scott Fitzgerald, and Hollywood greats Charlie Chaplin, Greta Garbo, Humphrey Bogart and Marilyn Monroe.
But what Petitti loves most about the place is that it still serves throwbacks to high-end cuisine of the past such as liver and onions, avocado cocktail and jellied consommé.
“You can go there and eat the kind of meal that Fitzgerald might have eaten. You can actually taste the past, which I think is absolutely fascinating,” Petitti says.
A trip to Tito’s Tacos for what is now — especially in L.A. — an outmoded version of a taco with its hard shell, ground beef, sliced or shredded cheddar cheese and iceberg lettuce, offers another path to explore the past.
“We tend to look down our noses at this classic American taco because now we want a homemade tortilla with what we now consider ‘authentic’ ingredients, probably served from a food truck,” Petitti says. But, he argues, it’s important to understand that this taco was created in the early-to-mid 20th century because Mexican immigrants to Southern California didn’t have easy access to the ingredients they would have had in their homeland.
“Again, it’s a passport to understanding a time and history and the ways that tastes adapt to circumstances,” Petitti says.
BUGS — THE FOOD OF THE FUTURE? If taste can transport us into the past, it can also project us into the future. Petitti thinks our culinary future will be based around alternative proteins, such as the “chapulines” — grasshoppers fried with chili and garlic and garnished with lime — that he takes his students to sample at “La Princesita” market in East L.A. “They seem like a novelty item to many people, but they also could represent the future of food,” he says.
Another way L.A. is exhibiting cutting edge practices around food, he says, is its leading role in popularizing sustainability and plant-based foods.
“I think what L.A. does in terms of food is so innovative,” Petitti says. “Look at Choi — born in South Korea but raised in L.A., he’s ostensibly a native son who takes Korean food and infuses it into L.A.’s most iconic and celebrated food item, the taco. That kind of innovation, and the fact that it’s affordable, represent L.A.’s approach to taste. It’s truly outstanding.”
THE BIOLOGY OF FOOD Speaking on Zoom from his home office, Grayson Jaggers, associate professor (teaching) of biological sciences, points out the four large, black ceramic crocks proudly displayed on his bedroom mantelpiece. They contain the fermenting miso his students made last semester during his course “The Biology of Food.”
In addition to exploring microbiology through the process of fermentation, his students learn about different concepts of genetics, the nature of mutation, evolution and how that relates to the production of genetically modified organisms.
One of Jaggers’ goals is to give his students — the majority of whom are not science majors — a broader appreciation for biology.
“The main thing I want students to get out of laboratory exercises like these is to try out new things and not be afraid of them,” he says.
HOW TASTE WORKS Jaggers points out that two elements are key to our perception of food: taste, of course, but also aroma. They are, he stresses, two very different things.
Taste is detected by receptors on our tongue that can bind certain chemicals, such as sugar and salt, which we perceive as sweet and salty tastes. Sour tastes originate in acids within the food. Umami (savory) taste, comes from glutamate, an amino acid that is one of the building blocks of protein. Bitter tastes, engendered by a wider range of molecules, signal to us that something is potentially toxic. This is why we inherently don’t like bitter foods, although bitterness can be an acquired taste.
“But if you say that something tastes sweet, that doesn’t tell you about the flavor, which might be chocolate or vanilla,” Jaggers says. “Flavor comes from aroma, while the sweet taste comes from sugar.”
Aroma in flavor is highly complex. Chocolate, for example, contains around 600 different molecules that work together to provide its flavor.
Volatile flavor molecules within food can also be released into the air, enabling us to smell dill or mint, for instance, without tasting it. Once we chew these herbs, what we taste is a more intense version of what we were smelling.
“Those same molecules that we were smelling are now being released into an area about the size of a postage stamp located in our nasal cavity,” Jaggers says. “Some 10 million different receptors in this area bind to those molecules, sending signals to the brain about flavor characteristics of that particular food.”
So, how do we learn to recognize and identify flavors? Conveniently, that area connects to a region called the limbic system near the forefront of our brain associated with olfaction and long-term memory.
Not surprising then that the taste of madeleines — small French sponge cakes — unleashed such a torrent of childhood reminiscences for Marcel Proust in his seminal novel, In Search of Lost Time.
Karen Tongson’s first question to students in her “Gender, Sexuality and Food Cultures” Maymester class is to identify and discuss their “Proustian moment” — that one taste that stands out in their life story.
Her own Proustian moment, she says, is the Kentucky Fried Chicken she tried for the first time in Honolulu after moving there from the Philippines with her family at age 4.
“I remember being blown away by how delicious it was, but I also remember the melancholy I felt because it made me realize I was very far from home.”
FINDING IDENTITY Tongson, chair and professor of gender and sexuality studies and professor of English, and American studies and ethnicity, also uses L.A. as a laboratory to teach about subjects that we can look at through the lens of food and taste — including gender and identity.
She argues that taste is how we formulate our sense of self.
“Taste extends across every realm of aesthetic experience,” she says. “So much of who we are and how we define ourselves is routed through our experience of taste, whether it’s food or how food aligns with our relationship to other aspects of our culture.”
Tongson notes that the first way we’re often introduced to each other — even before we may understand each other’s language or culture — is through each other’s food.
Through food, she says, we also discover similarities that might otherwise have gone unnoticed.
Angelenos, for example, share an affinity for food on skewers. “If you work your way through Historic Filipino Town and down Temple towards Alvarado and into MacArthur Park, you’ll find all sorts of foods being grilled on open fires and on skewers,” she says. “So, even if food is at first an encounter with the other, it eventually becomes an encounter with ourselves, as we come to find these shared and intersecting ways that we experience and taste life.”
Tongson says this is why taste is so important and so pleasurable to us — because it’s a gateway to our identity, a way of understanding ourselves in relation to the world.
“To taste is to have this profound and deeply tactile multisensory encounter,” she says. “The concept of taste also affirms who we are and how we’re perceived. It can be the gateway to a rich exploration of not only our personal histories, but of the places we live and the people who surround us.”
The Most Powerful Scents?
From aiding romance to communicating with God, scent has long been attributed near mystical abilities.
By Margaret Crable
Smell is, in many ways, the most magical and mysterious of the senses. It is what allows us to perceive something that is silent, invisible, can’t be touched and is frequently so unique it cannot be bottled or duplicated. The smell of your beloved, the scent of your child, the odor of a city you visited — all are complex and tantalizingly elusive, yet instantly recognizable and familiar. But — much as we might want to — they’re impossible to preserve for posterity, the way one might photograph a loved one or record their voice.
“Researchers have tried to find the smell that reminds people of home, but there isn’t one universal smell that works for everyone,” says Norbert Schwarz, Provost Professor of Psychology and Marketing.
In Western culture, scent is strongly associated with memory, capable of generating vivid flashbacks to past events. In a famed passage from In Search of Lost Time, Marcel Proust recounts how dipping a fragrant madeleine — a small French sponge cake — into lime flower-scented tea unlocks precious childhood memories, declaring: “…when nothing subsists of an old past, after the death of people, after the destruction of things, alone, frailer but more enduring, more immaterial, more persistent, more faithful, smell and taste still remain for a long time, like souls, remembering, waiting, hoping, on the ruin of all the rest, bearing without giving way, on their almost impalpable droplet, the immense edifice of memory.”
Scent’s ability to evoke the past is not its only power. From facilitating romance and seduction to communication with the divine, our sense of smell plays an outsized role in our emotional and spiritual worlds.
THE NOSE KNOWS It turns out, there’s an anatomical reason why smell seems so urgently powerful. Scent is the only primary sense that does not first get processed through the brain’s thalamus (known as the mind’s central processing unit) before being dispatched to the cerebral cortex for interpretation.
Instead, when we inhale a whiff of cedar or chocolate, this input is immediately sent not only to the olfactory and piriform cortex for interpretation but also to parts of our brain that process emotion, associative learning, memory and behavior — the amygdala-hippocampus complex. “No other sensory system has this direct and intimate connection,” says USC Dornsife’s Kurt Kwast, associate professor (teaching) of biological sciences.
The swift, involuntary reaction we have to certain scents is likely an evolutionary advantage. Stench, for instance, warns us of spoiled food, illness or death. The smell of smoke or rain, wafting toward human encampments long before the arrival of a forest fire or storm, can also be a first sign of danger.
Our aversion to the odors of rotting organic matter, that if fresh could otherwise have served as food, is so strong it transcends culture. Languages around the world possess an expression similar to the English phrases “something smells fishy” or “doesn’t pass the sniff test,” which align scents of decay with a feeling of suspicion.
Simply adding a rotten smell to a room has the power to alter human behavior, says Schwarz. “When we play economic trust games in the presence of a fishy smell, it reduces willingness to share by about 50%,” he says.
When subjects are asked questions that contain erroneous
statements in a well-ventilated room, many don’t notice, he adds. “However, if it smells fishy, you are more than 20% likely to notice something is wrong,” Schwarz says.
SCENT-IMENTAL REASONS Sweet scents, on the other hand, have been famed since antiquity for their ability to attract. In Greek mythology, the god Zeus, disguised as a white bull, seduced the princess Europa (after whom the continent is named) with an overpoweringly seductive aroma. Women in ancient Rome anointed their hair with perfumed oils and Cleopatra was said to smear her lips with such sweet scented oils, so that her lovers would be reminded of her all day.
In the Sanskrit epic of ancient India, the Mahābhārata, the fragrance of flowers is depicted as playing a central role in the founding of a dynasty.
But if smell in Western society has long been intricately linked with the evocation of memory, providing a pathway back to a former self, removed in time — although not necessarily in space — from the present, this notion was not shared by premodern Indians.
“People in medieval India thought scents please or displease, and correspondingly attract or repel. They’re not interested in the whole smell and memory thing,” says James McHugh, professor of religion. McHugh is the author of Sandalwood and Carrion, Smell in Indian Religion and Culture (Oxford University Press, 2012), which explores the olfactory sense in premodern India.
During the medieval period, India — where the sense of smell played a crucial role in daily life and religious ritual — was the hub of the aromatic world.
“Not only did the country produce many key ingredients,” McHugh says, “including sandalwood, saffron and cardamom, it was also at the crossroads of the trade in rare and exotic aromatics used to make costly perfumes, with cloves, nutmeg and camphor coming from Southeast Asia, frankincense and myrrh from the Persian Gulf and musk from the Silk Route to the north.”
During that period in India, the complex and creative use of aromatics was considered vitally important in enhancing pleasure to achieve an ideal love life, with perfumes of the period bearing deceptively avant-garde names such as Uproar, Moon Juice, Outrage and Who’s He?
Medieval Indian perfumes also provided a visual experience. Fragrances were diffused using pastes, tinted orange from saffron or white from camphor, rather than alcohol, which was not at that time used as a base for perfumes.
“Nowadays, you can’t tell if I’m wearing a scent. In medieval India, with perfume, you could see it. You would feel it on your body, everyone would see you wearing it, it was a multisensory experience,” says McHugh.
Ancient India was so taken with perfume that savoirfaire about how to mix and blend scents was akin to wine knowledge today — a sign of elite status.
“Educated people appear to have been far more interested in and articulate about smells than we are,” McHugh says. “Anyone who was anyone in premodern India had to have a fairly sophisticated knowledge about the art of perfumery.”
Medieval Indians were comfortable with the pungency of their natural environment. They also preferred high levels of aromatics, in sharp contrast with today’s Western society which, as McHugh observes, is often far more concerned with masking or removing odor than creating it.
That doesn’t mean we inhabit a scentless world, however. “Often when you wash your clothes or your dishes, you’re using perfume, although we don’t think, ‘I’m going to go put some perfume on my plates,’” says McHugh.
MY CHEMICAL ROMANCE A more intimate smell has recently emerged as a potential factor in human attraction: “pheromone-like” secreted or excreted chemicals that trigger a social response. The possibility that love — or at least sexual attraction — might literally “be in the air,” has not only engendered an ongoing cultural and scientific debate, but has unsurprisingly been seized upon by scent manufacturers. A roll-on perfume with a “pheromone elevation” became a Tik-Tok phenomenon last summer.
The science is still unclear, however, on how dominant a role personal odor actually plays in generating attraction, particularly considering humans lack the vomeronasal organ, or Jacobson’s organ, used by other mammals, as well as amphibians and reptiles, to interpret true pheromones.
However, small-scale studies have demonstrated that olfactory cues may still influence mate selection. A study in which women were asked to sniff shirts worn by men and then select the most attractive, found that they liked men genetically dissimilar to themselves.
Another study in which men sniff-tested cotton pads that women had used to swab their armpits found the men preferred the fragrance of women who were closer to ovulation and therefore more fertile.
“The idea of scent attraction is not mythical; there’s enough to suggest an association,” says Kwast. Of course, mate selection isn’t entirely down to smell. Other studies have found that people select mates whose faces most closely resemble their own, and lived experience shows us that people are attracted to others for a whole range of reasons beyond the physical.
HOLY SMOKES Scent has also long been associated with the divine. Incense is used in the worship of deities worldwide, from paganism to Buddhism to Christianity. Smoke from frankincense or sandalwood was thought to carry prayers up to heaven, a sentiment reflected in Psalm 141:2 of the Bible: “Let my prayer be set forth before thee as incense; and the lifting up of my hands as the evening sacrifice.”
A sweet-smelling church was an effective incentive to draw people to Mass by providing them with some relief from the unpleasant odors of an everyday life in which plumbing was largely nonexistent. Incense helped people envision what heaven might be like.
“For Catholicism, burning incense is partly about creating a ritual atmosphere that supports prayer and worship,” says Dorian Llywelyn, president of USC Dornsife’s Institute for Advanced Catholic Studies.
But incense and its sensual pleasures were also believed to have the power to disrupt. Early Christians denounced its use as pagan practice and, later, during the Protestant Reformation, incense was banned from churches, along with other “decadent” accessories like flowers and images.
“The Reformation thinkers were generally very distrustful of all the senses — except for hearing. Words were the big thing that counted, and they feared anything else would distract people’s religiosity and lead them into idolatry,” says Llywelyn.
Smell can also connote profound personal holiness. In 1918, Padre Pio, an Italian monk, was reported to have begun displaying the stigmata — marks resembling Jesus’ crucifixion wounds — while also emitting a strong perfume of violets.
The bodies of many Catholic saints, among them Saint Teresa of Avila, are reputed to have smelled of flowers after they died.
For Catholic believers, such stories seem to confirm that saints possess extraordinary holiness and show the truth of the Christian gospel of resurrection, which promises to restore the deceased to new life. “Such smells are almost a foretaste — a ‘glimpse through the nose’ — of what salvation would actually include,” says Llywelyn.
Parallels can be drawn with medieval India, where odors not only had the power to attract or repulse but were also considered indicators of virtue. Indeed, perfumes and aromatics, along with the sense of smell itself and other odors — both good and bad — were used as tools to create order in the universe as well as material and ethical hierarchies. Thus, for medieval Indians, the good and the godly literally smelled divine, while evil stank.
SAVED BY THE SMELL We’re still devising new ways to use the power of scent. Alumni Marat Zanov ’09 and Dawn McDaniel ’10, who both earned PhDs in psychology, added odors to their virtual reality program, which eases symptoms of PTSD in veterans by enabling them to relive past trauma in a safe environment.
Zanov, a former U.S. Air Force captain, notes the power of smell to take us back to moments of extreme stress.
“A veteran might be mowing his lawn on a peaceful summer’s day and suddenly the smell of gasoline from the lawn mower will trigger a flashback to a terrifying roadside bomb attack he experienced while serving in Afghanistan,” he says.
Incorporating such odors in the VR program, in which participants are guided visually through distressing memories, is an effective way to help participants relive painful episodes from their past in an effort to combat PTSD. Evoking the past through smell, Zanov and McDaniel argue, could help us heal for the future.
THE HUMAN TOUCH
From cradle to grave, touch brings us comfort, pleasure and sometimes pain, reminding us of our countless connections to the world and to humanity — including our own.
By Meredith McGroarty
Of all the heartrending phrases that came to define the deprivations of the COVID-19 pandemic, one stands out as particularly poignant: “skin hunger” — our visceral need for skin-to-skin contact.
Touch has the power to express or trigger countless feelings, from love, desire and comfort to menace, aversion or fear, often conveying the nuances of what our words cannot adequately voice. Perhaps then it is not surprising that touch is also the sense that philosophers and artists through the ages have embraced to define what it means to be human.
Aristotle believed that the sense of touch is what separates animals from plants, and its complexity in humans is what distinguishes us from other creatures. He posited that humans, lacking the tough hides, shells or hooves that protect other animals, often must rely on touch to keep us from harm: A scalding drop signals that the water is too hot; a sharp edge warns us to move away from a dangerous object.
During the Renaissance, Michelangelo’s depiction of the creation of Adam on the ceiling of the Sistine Chapel shows God reaching out to touch Adam’s outstretched finger, the contact signifying the origin of humanity itself.
One of our oldest and most ubiquitous social customs, shaking hands dates back to the fifth century BCE. What began as a way to signal that neither person was carrying a weapon was widely adopted as a symbol of peace and friendship and an expression of trust and good intention. It has long been echoed in expressions such as “staying in touch” and “losing touch.”
But in recent years, as we move into a progressively digital world where life is increasingly mediated through a screen rather than experienced directly, the hitherto primacy of touch faces challenges from artificial intelligence and haptic technologies, begging the question: Are we in danger of losing a significant part of what makes us human?
CHILDHOOD COMFORT There are some reasons to be optimistic. Skin-to-skin contact between infants and their parents is now widely recognized by pediatricians as vitally important in terms of bonding and development, although it’s still a relatively new concept for some European and North American cultures. Even after the age-old custom of dispatching babies to a wet nurse had largely died out in the West by the early 20th century, the prevailing attitude, that touching and holding children, especially boys, would render them “soft” and spoiled, persisted, says Darby Saxbe, professor of psychology and director of the Center for the Changing Family at USC Dornsife.
In fact, it wasn’t until the middle of the 20th century that animal experiments demonstrated that infant care entailed more than simply feeding a child to keep it alive.
In the studies, baby monkeys were given a choice between two maternal simulations, both made of wire. One simulation dispensed milk. The other didn’t, but was covered with soft cloth. The baby monkeys preferred the soft figure, even though it provided no food. This study and others, which showed how children who have a lack of physical contact with caregivers have more difficulty regulating emotions as adults, caused psychologists to shift course and stress the importance of touch and comfort in child development.
“The intentional approach of not being emotionally available to kids tends to backfire and create children and adults who are often more emotionally needy,” Saxbe says. “There is a world of research that has really confirmed that young children need a lot of closeness and comfort in the early years of life.”
THE CUDDLE SYSTEM But while recognition of the importance of touch in emotional development has led to pediatricians and psychologists promoting touch for young children and families, research shows that physical closeness is declining among adults.
Loneliness has become a newsworthy topic in recent years, with some experts classifying the trend as a health epidemic. According to former U.S. Surgeon General Vivek Murthy, “Loneliness and weak social connections are associated with a reduction in lifespan similar to that caused by smoking 15 cigarettes a day.”
But most people who discuss solutions to the issue of loneliness focus on medication and talk therapy and tend to ignore how physical proximity and touch — or the absence of it — affect mood, says alumna Sushma Subramanian. In her book, How to Feel: The Science and Meaning of Touch (Columbia University Press, 2021), Subramanian, who graduated in 2015 with degrees in political science from USC Dornsife and print journalism from the USC Annenberg School for Communication and Journalism, discusses several facets of the sense of touch, including how increased isolation has affected young people both romantically and socially.
Subramanian believes the increases in loneliness have been fueled by the general isolation of our modern world: Living alone has become more common; friends gather less frequently, both due to the pandemic and the prevalence of the internet; and touch occurs mostly between romantic partners. Add to this the fact that an increasing awareness of personal boundaries has resulted in a decrease in casual or friendly touching, especially for men, and you have a difficult situation, she says.
“The truth is we’ve created very limiting conditions for a lot of people to receive touch,” Subramanian says. “Men can basically not touch unless they’re in a romantic relationship or playing sports. It’s more acceptable for women to touch each other, so maybe they’re missing it less. But there are many limits on who gets to touch and when, depending on identity and class.”
Returning to an age when people were expected to put up with unwanted touching is obviously not the answer, Subramanian says, but she notes that people have found some ways to increase physical contact in a positive way. She believes that one such response is the popularity of activities such as yoga, which encourage a positive awareness of and relationship with one’s body. A number of groups have popped up online for people interested in gathering for platonic hugging and touching, and it is possible the future might see a rise in “professional cuddlers” who can provide nonsexual comfort or contact.
“Professional cuddling has been very valuable for a lot of people,” Subramanian says. “Some told me that by developing that practice of touch through a professional cuddler, they felt more confident going out in their lives and having romantic relationships and interactions.”
IMAGE SOURCE: ISTOCK BLOCKING THE PAIN But touch does not simply exist in the emotional sphere; it is essentially a physical function. And one of its responses — pain — is at once essential for protection in some circumstances (for example, a signal to move one’s hand away from a hot stovetop) and detrimental to a person’s functioning in others. Understanding how and why we feel pain is an area of expertise for USC Dornsife’s David McKemy, professor of biological sciences, whose research explores how temperature regulation is linked to pain responses.
Previous research using capsaicin — found in chili peppers — has examined the function of a bodily protein that senses heat. McKemy’s research instead uses menthol — found in mint — to study how the body responds to cold. He is particularly interested in how a menthol receptor, which is a cold-sensing protein, functions in individuals with chronic pain conditions, such as migraines.
“A number of genome studies have looked for genes that might be associated with migraines, and one particular menthol-sensitive protein that enables us to detect cold temperatures keeps popping up in every single one of these studies,” he says. “People who have a specific mutation in this gene are more likely to have migraines and are more sensitive to cold because they make more of this protein. Another mutation in which individuals make less of this cold-sensing protein means those people aren’t as likely to have migraines and can’t sense cold as well.”
In addition to migraines, McKemy is interested in how chronic pain develops. For example, women undergoing treatment for breast cancer often report feeling pain when they come into contact with something cool, a side effect of the toxicity of chemotherapy. When there is damage or injury to part of the nervous system, McKemy has found that a small protein is released that interacts with the menthol receptor to increase its sensitivity to cold, causing pain. Blocking the function of this protein can specifically prevent this type of pain that occurs after injury, he notes.
“We’re focusing on understanding how these particular proteins might play a role in migraines and the chronic cold pain that people get in different conditions,” McKemy says. In the future, the research may help prevent or better treat these types of cold-related pain.
A NEW SENSATION While McKemy’s research seeks to identify the intricacies of sensation, USC Dornsife’s Andrew Hires is working on the topic from another angle: how to restore the ability to feel and touch in individuals who have lost it. Hires, assistant professor of biological sciences, is working with mouse models to identify how the brain senses the location of objects and how this translates into sensations of touch.
“I’m looking at how forces of touch are represented by patterns of electrical activity within the cortex of the brain,” Hires says. “There’s some integration that takes place, where the motion of the touch sensor, like fingers on a surface, has to be combined somehow with the signals coming from the fingers.”
Hires’ research looks at how mouse whiskers, which function similarly to fingers in humans, send signals to the brain when they move across an object or bump into a surface. Looking at how the cortex of the brain processes these signals, researchers observe patterns in brain activity that correspond to different perceptions or sensations of surfaces and objects. Then, by looking only at those brain patterns, researchers can deduce the positioning of an object encountered by the mouse.
“When we look at how touch perception is represented in the brain, we find there’s a lot of variation — or plasticity — in the activity patterns,” Hires says. “By observing the neurons turned on at any given time and studying how they change, we hope to determine the rules that govern this reorganization and relearning of particular touch perceptions.”
If we understand the neural patterns the brain makes in response to certain sensations, it may be possible to help “retrain” the sense of touch. This could benefit survivors of strokes who suffer from paralysis by reprogramming the brain to receive sensations from the paralyzed body part. Understanding cortex signals could also help “connect” the brain with artificial hands or feet, helping amputees restore feeling.
“So, an amputee could be fitted with artificial fingers that can ‘feel’ the surfaces of things,” Hires says. “This would work by stimulating particular nerve patterns within the remaining, biological arm. The brain can relearn to interpret those patterns in order to reawaken the ‘sensation’ of fingers in the prosthetic hand.”
ONCE MORE, WITH FEELING Aristotle’s theory that touch is what sets humans apart from animals or plants may be scientifically incorrect — he had no way of knowing that one day science would show that the genomes of chimpanzees and humans are 96% identical. However, in highlighting how essential the sense is, and how it connects to the complexity of human emotions, his theory continues to present a strong metaphysical argument for what makes us human.
“We live in bodies that are most alive when they’re open and permeable to what is around us,” Subramanian writes.
When the handrail wobbles, we know to exercise caution in the face of potential danger; a hug from a family member conveys love and comfort; the cool caress of a silk blouse is synonymous with luxury; plunging our fingers into damp earth to plant a seed makes us feel in tune with nature.
“Touch is a constant affirmation that we exist as selves, separate from our surroundings but connected to them,” Subramanian writes in the conclusion of her book.
And perhaps that is the aim of every human being — to live a life full with feeling.
