Given its distance from the brain, neuroscience hasn’t had much to do with the heart quietly thumping in your chest. But to get a fuller picture of the mind, you need to start looking below the neck.
These matters of the heart are University of Sussex researcher Sarah Garfinkel’s speciality. Her recent work has built a strong case that both emotion and cognition are “embodied”: Over the past several years, she’s found evidence that the beats of your heart — and your awareness of that rhythm — shapes everything from anxiety to racism to stock trading.
Every time the heart projects blood, it pings pressure-sensitive receptors that send signals to the head. “The brain essentially flashes each time the heart beats,” she says, “and the degree of signal in the brain corresponds to how fast and how hard the heart is beating, so the brain is in dynamic, constant communication with the heart,” especially the amygdala and thalamus, regions associated with fear and pain perception, among other roles. Yes, she tells Science of Us, your brain is your brain, but it also represents the activity of our organs, and whether you realize it or not, these sensations guide the way you navigate the world. Recognizing this marks a shift in how neuroscience could be approached, she says: Rather than separating the brain and the body, the brain is seen as embedded within the body. Doing so could offer new treatments for things like anxiety, where drugs could target bodily processes as well as those in the brain, or behavioral techniques like meditation that make people more bodily aware.
“I think the general public kind of knows it instinctively, they know if they exercise they feel better, they know their mood changes, their cognition and memory increases; people who meditate also see changes in their cognition and emotion,” she told Science of Us at this year’s meeting of the Society for Personality and Social Psychology. “It’s a responsibility of the scientific community to better understand these mechanisms and promote them as scientific — I feel instinctively that there’s a split where people think there are ‘scientific treatments’ like drugs, and there’s these ‘alternative treatments,’ and why do we need the distinction? If we can look at body-brain mechanisms, they can be scientific treatments as well — we just don’t yet know the mechanisms.”
One of those primary somatic tools is interoception, or the felt sense of the activities of your organs. Following in the tradition of William James, Garfinkel (and other neuroscientists and social psychologists) are finding that bodily sensations are key ingredients in emotional experiences, and that how fine-tuned of an internal “feeler” you are predicts your ability to stabilize them (which is part of why, I’ve been told, yoga helps develop emotional intelligence). Yet, as Garfinkel and her colleagues showed in a 2015 study, being confident about your interoceptive ability does little to imply your accuracy on an interoceptive accuracy task, like counting your heartbeats through a 25-to-50-second block of time.
That gap looks to have big consequences for well-being. In a 2016 paper, Garfinkel and her colleagues recruited 20 people with a diagnosis of autism and 20 control participants. They self-reported how confident they were about their interoception and took accuracy tests, plus tests for anxiety, severity of autism, and emotional sensitivity. The people with autism self-reported being really good at interoception, but their tested performance was poor. With that, Garfinkel and her colleagues wrote, “a positive relationship emerged”: The greater the overestimation, the greater the state and trait anxiety scores. The bigger the disconnect between self-conception and physical sensation, the greater the anxiety.
Garfinkel says her team decided to study people with autism because the condition is so often accompanied by anxiety, but this “interoceptive trait prediction error” can happen more or less in anybody. Like, recall the last time you felt socially awkward at a friend of a friend’s birthday party. You shuffle toward the drinks, pick at your fingernails, feel your heart pumping. Having that thumpy sensation emerge in your awareness is a signal from your chest to your head: “If it passes a threshold so you feel your pounding heart, then that is a cue,” she says, and “it’s good to know how to potentially respond to it.” (Pro tips: Breathe deep, recognize it’s just a sensation, and make associative conversation with the nearest interesting person.) That’s the risk of not being able to tap into your somatic signals: “Then you have unaccounted-for bodily sensations,” she says, “which can come out as anxiety.”
Conversely, high interoceptive fluency can also help you make a lot of money. In another 2016 paper, Garfinkel and her colleagues recruited 18 male high-frequency traders from the London Stock Exchange. They and a control group did the heartbeat-detection tasks, and the traders outperformed their non-financial peers. That’s maybe a little surprising, but not as much as the follow-up findings: the traders’ heartbeat-counting-task scores predicted their average daily profitability over the previous year, and it also predicted the number of years he survived as a trader. It’s a small study, but even so, it provides pretty compelling evidence that decision-making is an emotional, physiological process. “Traders in the financial world often speak of the importance of gut feelings for choosing profitable trades,” the researchers wrote. “By this they mean that subtle physiological changes in their bodies provide cues helping them rapidly select from a range of possible trades the one that just ‘feels right’. Our findings suggest that the gut feelings informing this decision are more than the mythical entities of financial lore — they are real physiological signals, valuable ones at that.”
The traders and the people with autism show two different ways to access the interoceptive pathway from the body to the brain. The traders experiment looks at interoceptive accuracy, a process impaired in autism. If the trader process is indeed gut instinct, Garfinkel explained in a follow-up email, that process tends to be emotionally loaded — the decision feels right or good. “This is a fast source of affective (emotional) information not accessible to people with autism,” she added.
Alas, not all affairs of the heart are so warm and positive. Garfinkel has also found that fear responses to scary faces are amplified when presented at cardiac systole, or when the heart ventricles contract. This may have behavioral and political consequences: In a just-published paper, Garfinkel and her colleagues found that the negative racial stereotype of identifying black people with threat is exaggerated at systole, where participants were more likely to say that a black man holding a phone or a wallet was holding a gun. The authors reasoned that “in the context of alertness to threat-signalling stimuli, heightened representation of cardiac signals in the brain may enhance the salience of social cues and promote the expression of negative racial stereotypes.” More hopefully, heartbeat awareness looks to be trainable: Garfinkel says she has yet-to-be-published data suggesting that you can teach people to align their interoceptive self-confidence and their accuracy, reducing the unrecognized sensations and the anxiousness they promote, which rhymes with how increasing awareness of the breath through meditation reduces anxiety. It’s a poetic finding, really: Know your heart, ease your mind.