There is the famous five, then there is the sense most people rarely think about at all.
Researchers are paying closer attention to interoception, the body’s ability to sense and interpret internal signals like heart rate, breathing, hunger and temperature. Psychologists Jennifer Murphy of Royal Holloway University of London and Freya Prentice of University College London wrote in The Conversation in 2022 that it is “an extremely important sense as it ensures that every system in the body is working optimally”.
“It does this by alerting us to when our body may be out of balance, such as making us reach for a drink when we feel thirsty or telling us to take our jumper off when we’re feeling too hot,” they wrote.
Researchers are now beginning to think interoception may do more than regulate biological needs. The article says it may play a part in mental health conditions including anxiety, depression, PTSD and eating disorders.
The general idea, the article says, is that awareness of muscle tension, breathing and heart rate can give people clues about when a situation is “safe” or “unsafe”. When that process is interrupted, it could contribute to mental health conditions.
Murphy and Prentice’s 2022 analysis of 93 studies found that interoception differs significantly between men and women, with women showing lower accuracy on heart-based tasks in particular. They wrote that this may partly explain why conditions like anxiety and depression are more prevalent in women than men from puberty onward, while stressing the relationship is complex and not fully understood.
An experiment published in eBioMedicine this year looked at how hunger affected mood. It showed that people with strong and accurate interoception experienced fewer mood swings than those with poor interoception.
“This does not mean they never felt hungry – they just seemed better at keeping their mood levels stable,” medical psychologist and corresponding author Nils Kroemer from the University of Tübingen in Germany wrote for The Conversation.
Research on people with anorexia nervosa by scientists at UCLA has also been cited as strong evidence. The researchers tested interoception with an ingestible vibrating pill and found that people with anorexia had difficulty detecting internal hunger signals, even after they put weight back on.
“People with anorexia nervosa do not simply ignore signals from the body,” said Sahib Khalsa, the study’s senior author and a neuroscientist at UCLA.
“Rather, their nervous system may process gut sensations differently, making those signals harder to detect, trust and learn from. Over time, that may contribute to the persistence of symptoms even after weight is restored.”
Not everyone agrees with how the field uses the term. An opinion piece published in Frontiers in Psychology in 2024 argued, “There is no such thing as interoception”.
The authors, led by cognitive scientist Felix Schoeller from MIT, said the title was intentionally provocative and argued that researchers may be grouping many different factors under one broad label.
“While the title of this article is intentionally provocative, it serves to highlight a critical issue in the field: namely that the term ‘interoception’ is often used in ways that belie the complexity and diversity of the phenomena it purports to describe,” the team wrote.
The article also notes that Barry Smith from the University of London claims humans actually have up to 33 different senses.
“Better understanding all the factors that affect interoceptive ability may be important for someday developing better treatments for many mental health conditions,” wrote Prentice and Murphy.
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