You think you have five senses.
That’s the story we’re told. The one drilled into us in kindergarten with the song.
It’s not the whole story.
Research keeps piling up, pointing toward a sixth sense. One that regulates your biology and likely your mood, too. Almost nobody mentions it. Yet it might matter as much as sight or touch for keeping you sane.
We call it interoception.
Listening In
It’s the body’s ability to hear itself.
Not sound, literally. But the raw data. Your heart pounding. The diaphragm rising and falling. The burn of hunger or the flush of heat spreading under your skin. These signals fire constantly, invisible and ignored until they scream.
Psychologists Jennifer Murphy and Freya Prentice called it essential in 2022 without being flashy about it.
It ensures every system in the body is working optimaally by alerting us to imbalance.
Simple, right? Thirst means drink. Hot means remove the sweater. Homeostasis.
So far.
The plot thickens when you look at mental health. This internal monitoring system doesn’t just fix your temperature. It might be diagnosing safety in real time. Is this room dangerous? Is my heart rate spiking for no reason? The signals are subtle—muscle tension, breath depth, pulse—but they shape your emotional landscape.
Break the link and the house gets shaky.
Anxiety is one result. Someone sits in a meeting and their heart kicks. Instead of ignoring the physical noise, they interpret it as threat. The signal says “unsafe.” The mind agrees. The spiral starts.
Gender plays a role, too.
A 2022 review of 93 studies by Murphy and Prentice showed a distinct difference. Women often scored lower on tasks measuring heart-rate awareness. The researchers linked this to higher rates of anxiety and depression in women after puberty. It’s messy. Not causal. Just a complex thread in the fabric of why we feel the way we do.
Hungry and Happy
Hunger isn’t just physical.
Or so Nils Kroemer suggested this year in eBioMedicine.
He looked at mood swings and starvation signals. People with sharp interoception kept their mood stable despite the gnawing emptiness in their stomachs. Those who couldn’t feel the signal clearly swung wildly in emotion.
They didn’t go without hunger. They just kept the levels steady.
It’s a buffer. A grounding wire.
The Ghost in the Machine
The most chilling evidence comes from UCLA.
Specifically, from scientists studying anorexia nervosa.
The assumption is usually willpower. That these patients choose to ignore their bodies. The data suggests something colder.
Their nervous systems don’t hear the signal.
Researchers used an ingestible vibrating pill to test this. The gut was stimulated directly. Patients with anorexia still struggled to perceive the sensation, even after regaining weight.
Sahib Khalsa, the neuroscientist behind the study, was clear.
They do not simply ignore signals. The nervous system processes them differently. Harder to detect. Harder to trust.
So the symptoms stick. Not because of stubbornness. Because of broken hardware.
Maybe It’s Not A Thing
Then came the pushback.
2024 brought a provocative essay in Frontiers in Psychology. Felix Schoeller from MIT and his team declared a bold falsehood for effect.
“There is no such thing asinteroception.”
Clickbait title, sure. But the point stuck.
The argument is that we’re throwing everything under one banner. Digestion. Balance. Temperature. Proprioception. It’s too broad. Too simple. We are labeling a constellation of diverse mechanisms with one sticky word.
Barry Smith from University College London agrees, taking it further.
We don’t have five senses. Or six.
We have up to 33.
The line is blurry.
What we do know is that the map of human perception is incomplete. We underestimate what we can feel. These unnamed or poorly named senses are running the show, influencing health and mind in ways we’re just beginning to sketch.
Murphy and Prentice see the utility in this chaos. Better understanding of these signals could lead to better treatments.
Maybe the diagnosis wasn’t wrong all along. Just the definition.
