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About a quarter of the human brain’s mass is devoted to processing information from the five senses. Given that the brain plays such a central role in health, it’s not surprising that the five senses are closely tied to well-being.
But beyond merely proving those connections exist, researchers have recently started to explore ways to purposely manipulate them for people’s benefit. “Interventions based on what we see, feel, and even taste can have a seemingly dramatic effect on health,“ says Charles Spence, an Oxford University PhD researcher who runs a lab dedicated to studying the role that perception plays in behavior and health. “They can reduce pain, speed recovery from illness, and much more.”
Smell plays an important role in overall health. “Smell is associated with neurodegeneration, heart disease, and early demise, among other problems,” says Richard Doty, a PhD smell researcher who directs the Smell and Taste Center at the University of Pennsylvania’s medical school. Doty notes that multiple studies have shown that people whose sense of smell becomes heavily dulled over time are at a higher risk for those diseases. In the case of Alzheimer’s, clumps of protein known as plaques that build up in the brains of people who suffer from the condition form in the part of the brain responsible for smell, possibly explaining the association.
Paying more attention to smell could provide a critical early tipoff to brewing problems. A decline in your sense of smell is as good a predictor of Alzheimer’s as genetic tests, according to Doty. To test how useful that relationship can be, in 2020, Doty will send 80,000 people a smell test he developed as part of a study funded by the Michael J. Fox Foundation. People whose results on the test indicate that they’re losing their sense of smell can be tagged for brain imaging and other advanced tests for neurodegeneration. If the effort helps catch problems early — when diseases of the brain may be more treatable — promoting smell awareness could become a major public health initiative, says Doty.
The sense of touch is getting a closer look, too. Research shows that people in stressful situations tend to touch their faces more often. In addition, Joshua Ackerman, a PhD psychology researcher at the University of Michigan, has studied the impact of face-touching on decision-making. He’s learned that people touch their faces an average of about 15 times an hour, and they say it clarifies thoughts and feelings. “Just putting your hand up to feel your face at some level directs your attention toward what’s going on in your head,” he explains. “The same areas of the brain that process information from the senses also deal with other types of thoughts and actions. So the processes can spill over and influence one another.”
“Stroking the skin at a rate of two to four inches per second appears to produce the biggest positive effect. ‘We’re starting to bring scientific rigor to what has traditionally been a touchy-feely area, if you’ll excuse the pun.’”
Ackerman conducted a study in which he found that merely touching an object can influence people’s attitudes. What happens, he explains, is that the feel of an object can trigger associations to specific thoughts and emotions. Holding a heavy object may conjure a feeling of gravity, for example. “The sensations trigger metaphorical ways of thinking,” he says.
Putting these learnings to work is tricky, admits Ackerman, because like many unconscious effects, they tend to disappear when you tell people about them. Thus simply advising people to touch their faces to reduce stress or lift a lightweight object if they want to feel more easygoing might not work.
But there are other ways people can benefit from touch. Oxford’s Charles Spence — who is writing a book called Sense Hacking, to be published early next year — recently identified specific types of caressing (of the arm and other areas of the body) that are linked to feelings of well-being. The research found that stroking the skin at a rate of two to four inches per second appears to produce the biggest positive effect. “We’re starting to bring scientific rigor to what has traditionally been a touchy-feely area, if you’ll excuse the pun,” he says.
Spence advises anyone recovering from an illness to embrace caresses, whether from family, friends, or care providers, as a way of speeding up recovery. His one qualification: Make sure the stroking is performed by a human being. “There have been efforts to create the same sensations with a robot’s touch,” he says. “But they don’t have the same effect. We don’t know why, but there’s something about human interpersonal touch that has special properties.”
Spence studies the impact of sight on health, too. His lab has found, for example, that people who are told to look at their painful wounds and injuries through a “minimizing lens” — essentially a pair of binoculars turned backwards to make things look smaller — experience notable improvements not only in pain, but even in swelling and other physiological symptoms. It sounds bizarre, but Spence offers a simple explanation: “A big wound hurts more than a small one, doesn’t it?” Convincing part of the brain that the wound is smaller may trigger changes in both pain perception and the immune system.
Another sight-based phenomenon Spence’s lab uncovered addresses the problem of undernutrition among elderly people. Studies have found that getting older people to eat a bit more each day cuts their risk of dying during a hospital stay in half. Spence’s group showed that by simply using brightly-colored plates and flatware, they were able to increase older people’s food consumption as much as 30%. It’s not entirely clear why the gimmick works, but Spence says it may turn eaters’ attention to the meal. “It works just as well back at home as it does in the hospital,” Spence says.
Spence is also considering ways to use hearing to people’s advantage. He’s specifically interested in building on the well-established finding that music assists in healing, largely because music reduces stress and anxiety. Spence speculates that the soothing powers of music are heightened if music is specifically curated to address different types of illness — such as one playlist for someone recovering from heart surgery, and another for a person receiving chemotherapy. Research has demonstrated that physical-therapy patients do better when certain sounds are played at specific points during the therapy. “Playing a nice, harmonious sound in synchrony with patients flexing their backs leads to much better flexibility than when the sound of a creaking door is played,” he says.
Ravi Mehta, a PhD consumer psychology researcher at the University of Illinois at Urbana–Champaign, has found that sound doesn’t have to be harmonious to bring benefits. Studies have shown the impact of noise can vary with the type of noise, the volume of the noise, and the type of thinking. To tease some of the effects apart, Mehta and colleagues exposed people in a study to different types of noisy soundtracks while asking them to perform various tasks. The results suggested that when people need to be creative, just the right amount of noise can win the day. The brain easily filters out a bit of noise, and becomes impaired by a lot of it, but is most productive when there’s a medium amount. “If you need to think more broadly, then noise helps,” he says.
The reason it works, Mehta speculates, is that the noise may “defocus” the brain, forcing it out of whatever rut it may be in and freeing it up to explore new avenues of thought. Mehta now wants to pin down specific aspects of the noise, such as tempo and pitch, that might fine-tune the benefits. For now he recommends working in coffee shops, but he also offers a warning. “Noise can make things worse if you need to focus in on routine details,” he says. “A coffee shop is probably not a good place to do your taxes.”
Eighty percent of what the brain interprets as a taste sensation is in fact really coming from our sense of smell. For that reason, researchers usually focus on smell as the more important input, even when it comes to what we put in their mouths. Not only do people smell food through their noses, but we smell it even more strongly when we place it on our tongues and particles from the food waft back in our mouths and into our nasal passages.
Studies suggest people can differentiate between as many as a trillion different odors, but taste — when smell is taken out of the picture — is in comparison a blunt instrument, capable only of picking out five different inputs: saltiness, sweetness, bitterness, sourness, and savoriness (sometimes called “umami.”) You might think that would leave little opportunity for manipulating taste in the interests of better health. But in fact, there are a few techniques that are proving useful.
One is the reassuring power of sweetness. For centuries parents and care providers have given sugar and other sweets to children in order to distract them from things like a painful shot, or as a reward. The phenomenon turns out to work just as well in adults. Spence conducted an experiment where he asked students to plunge their arms into an ice bath. The students reported significantly less discomfort when they were given some sort of sweet-tasting food just before the plunge. “Strawberries, caramel, and vanilla seem to work as well with adults as sugar does with babies,” he says. “And there’s evidence it applies in clinical settings in the same way.” That doesn’t mean a person must be exposed to ice or a needle to get the benefits of sweetness, he adds. A sweet taste appears to generally mitigate physical discomfort or unease.
Bitterness may also come in handy for health. Research at Rutgers University has shown that people who are more sensitive to bitter tastes tend to be more selective about what they eat, and often end up with healthier diets that are lower in sugar and fats. While it hasn’t yet been proven, researchers have speculated that this and similar findings on taste sensitivities might be put to use by adjusting the flavor intensity in foods so that healthier foods become more appealing. But research like that is many years down the line.
The sensory approach to health and wellness is still in its early days, and there’s much for researchers to tease out and clarify. But in most cases there’s little cost and virtually no risks or side effects involved in experimenting with them on your own. Go ahead and head to the nearest coffee shop for better productivity, or get a massage if you’re feeling blue. It might help, and certainly won’t hurt.