Your Brain Is Guessing About Your Body, and the Guess Becomes a Feeling

Stand backstage before a talk and notice what happens. The heart speeds up, the stomach tightens, the hands go slightly cold. Nothing in those signals announces itself as dread rather than eagerness, yet within a second or two you will have decided which one you are having. That small, almost invisible act of interpretation sits at the center of a body of research suggesting that conscious experience is less a report on the body and more a running set of predictions about it.

The technical term for the sensing side of this process is interoception. Researchers use it to describe how the nervous system detects, transmits, and interprets signals arising from inside the body, including cardiac, respiratory, gastric, thermal, and immune information (Quadt et al., 2018). In plainer language, it is the channel through which the brain keeps track of its own machinery. It is distinct from exteroception, which handles the outside world, and from proprioception, which tracks where your limbs are in space, though all three feed the same interpretive system.

What makes the recent work interesting is the direction of traffic. Under predictive processing accounts, the brain is not waiting passively for bodily news to arrive and then reacting. It generates descending predictions about what its internal state should be, compares those predictions against incoming signals, and treats the mismatch, called prediction error, as the thing worth paying attention to (Barrett & Simmons, 2015). Seth (2013) extended this logic specifically to the body, proposing interoceptive inference as an account of emotion and of the felt sense of being a self. Emotional content, on this view, reflects the brain's best explanation of why the viscera are doing what they are doing.

There is a further step that I find genuinely clarifying. In active inference, prediction error can be reduced in more than one way: the brain can update its model, or it can change the world so the prediction comes true. For interoception, that second route runs through the autonomic nervous system, meaning that autonomic reflexes can fulfill interoceptive predictions much the way motor reflexes fulfill proprioceptive ones (Seth & Friston, 2016). Your heart rate is not only evidence about your state; it is also an instrument the model uses to make itself correct. Regulation and representation stop being separable jobs.

That reframing brings allostasis into view. Homeostasis is the familiar idea of holding internal variables near a set point, correcting deviations after they occur. Allostasis refers to anticipatory regulation, adjusting physiology in advance of predicted demand rather than waiting for the error (Quadt et al., 2018; Quigley et al., 2021). Someone who wakes at 6:20 every morning with cortisol already rising before the alarm is a small illustration; the body has budgeted for a day that has not started yet. Quigley and colleagues (2021) argue that this energy-regulatory function is foundational, and that the experience of having a self emerges from it rather than sitting alongside it.

Carvalho and Damasio (2021) push the point toward phenomenology, describing feelings as conscious mental events that represent body states under homeostatic regulation. Feelings, in that framework, are not decorative accompaniments to physiology. They are how the state of the interior becomes available to the rest of the mind, which is a strong claim and worth flagging as a theoretical synthesis rather than a settled empirical result. The proposal that continuity of internal sensing across a lifetime underwrites a unitary sense of self is likewise a model, not a demonstrated mechanism.

Neuroanatomy gives the account somewhere to live. The anterior insula appears repeatedly as an interface where bodily appraisal, emotional awareness, and social behavior converge (Garfinkel & Critchley, 2013; Critchley & Garfinkel, 2017). Lesion and imaging work has made it a natural candidate for the site where visceral information becomes something like a feeling, though attributing a construct as broad as emotional awareness to one region is the kind of shorthand that flattens real complexity.

Measurement is where things get usefully complicated. Garfinkel et al. (2014) showed that interoception is not one ability but several dissociable dimensions: interoceptive accuracy, meaning objective performance on tasks such as heartbeat counting; interoceptive sensibility, meaning self-reported belief about how attuned you are; and interoceptive awareness, meaning the correspondence between the two, essentially metacognitive insight. People can score high on one and low on another, and that gap seems to matter. In autistic adults, discrepancy between accuracy and sensibility correlated with emotion sensitivity difficulties and anxiety symptoms (Garfinkel et al., 2016). Correlational, modest samples, so the direction of influence remains open.

Timing effects offer a different angle. Words presented at cardiac systole, the moment the heart contracts and baroreceptors fire, were remembered less well than words presented at diastole (Garfinkel et al., 2013). A cognitive outcome shifted with the phase of the heartbeat, which is difficult to explain if bodily signals are merely background noise. Pharmacology adds another line: acute citalopram reduced posterior insula and amygdala responses to attended visceral sensation, while anterior insula effects depended on participants' anxiety levels (Livermore et al., 2024).

The clinical implications are being actively pursued rather than established. Nord and Garfinkel (2022) map interoceptive pathways as potential targets for mental health treatment, and Bonaz et al. (2021) catalogue the disorders and comorbidities in which interoceptive dysfunction appears, from functional gastrointestinal conditions to chronic pain and anxiety. Whether interoceptive training changes symptoms durably is not yet answered. It seems plausible, and the mechanistic story is coherent, which is not the same as evidence of benefit.

Here is what I think the framework buys a reader. Once you take seriously that feeling is a prediction rather than a readout, the backstage heartbeat stops being a verdict and becomes a piece of ambiguous data your brain is already busy explaining. That does not make anxiety a mistake, and it would be glib to suggest otherwise. It does mean the interpretation has moving parts, and moving parts are the sort of thing that can sometimes be studied, sometimes shifted, and at minimum named.

References

Barrett, L. F., & Simmons, K. (2015). Interoceptive predictions in the brain. Nature Reviews Neuroscience, 16, 419-429. https://doi.org/10.1038/nrn3950

Bonaz, B., Lane, R., Oshinsky, M., Kenny, P., Sinha, R., Mayer, E., & Critchley, H. (2021). Diseases, disorders, and comorbidities of interoception. Trends in Neurosciences, 44(1), 39-51. https://doi.org/10.1016/j.tins.2020.09.009

Carvalho, G. B., & Damasio, A. (2021). Interoception and the origin of feelings: A new synthesis. BioEssays, 43. https://doi.org/10.1002/bies.202000261

Critchley, H., & Garfinkel, S. (2017). Interoception and emotion. Current Opinion in Psychology, 17, 7-14. https://doi.org/10.1016/j.copsyc.2017.04.020

Garfinkel, S., Barrett, A., Minati, L., Dolan, R., Seth, A., & Critchley, H. (2013). What the heart forgets: Cardiac timing influences memory for words and is modulated by metacognition and interoceptive sensitivity. Psychophysiology, 50, 505-512. https://doi.org/10.1111/psyp.12039

Garfinkel, S., & Critchley, H. (2013). Interoception, emotion and brain: New insights link internal physiology to social behaviour. Social Cognitive and Affective Neuroscience, 8(3), 231-234. https://doi.org/10.1093/scan/nss140

Garfinkel, S., Seth, A., Barrett, A., Suzuki, K., & Critchley, H. (2014). Knowing your own heart: Distinguishing interoceptive accuracy from interoceptive awareness. Biological Psychology, 104, 65-74. https://doi.org/10.1016/j.biopsycho.2014.11.004

Garfinkel, S., Tiley, C., O'Keeffe, S., Harrison, N., Seth, A., & Critchley, H. (2016). Discrepancies between dimensions of interoception in autism: Implications for emotion and anxiety. Biological Psychology, 114, 117-126. https://doi.org/10.1016/j.biopsycho.2015.12.003

Livermore, J. J. A., Skora, L. I., Adamatzky, K., Garfinkel, S. N., Critchley, H. D., & Campbell-Meiklejohn, D. (2024). General and anxiety-linked influences of acute serotonin reuptake inhibition on neural responses associated with attended visceral sensation. Translational Psychiatry, 14. https://doi.org/10.1038/s41398-024-02971-3

Nord, C. L., & Garfinkel, S. (2022). Interoceptive pathways to understand and treat mental health conditions. Trends in Cognitive Sciences. https://doi.org/10.1016/j.tics.2022.03.004

Quadt, L., Critchley, H., & Garfinkel, S. (2018). The neurobiology of interoception in health and disease. Annals of the New York Academy of Sciences, 1428. https://doi.org/10.1111/nyas.13915

Quigley, K., Kanoski, S., Grill, W., Barrett, L. F., & Tsakiris, M. (2021). Functions of interoception: From energy regulation to experience of the self. Trends in Neurosciences, 44, 29-38. https://doi.org/10.1016/j.tins.2020.09.008

Seth, A. (2013). Interoceptive inference, emotion, and the embodied self. Trends in Cognitive Sciences, 17(11), 565-573. https://doi.org/10.1016/j.tics.2013.09.007

Seth, A., & Friston, K. J. (2016). Active interoceptive inference and the emotional brain. Philosophical Transactions of the Royal Society B: Biological Sciences, 371. https://doi.org/10.1098/rstb.2016.0007