We have many more than five senses

We're all familiar with the phrase "healthy body, healthy mind". But this doesn't just refer to physical fitness and muscle strength: for a healthy mind, we need healthy senses, too.

Fortunately, there's now a wealth of evidence that we can train our many senses, to improve not only how we use our bodies, but how we think and behave, as well as how we feel. Trapped as we are in our own "perceptual bubbles", it can be hard to appreciate not only that other people sense things differently — but that so can we, if we only put in a little effort.

But if we're going to make the most of using and improving our senses to enhance our wellbeing, we have to consider more than sight, hearing, taste, touch and smell. Aristotle's desperately outdated five sense model may still be popular, but it vastly under-estimates our extraordinary human capacity for sensing.

Proprioception

Proprioception — the sensing of the location of our body parts in space — has been relatively ignored, but it's critical for confidence in using our bodies. If you now shut your eyes, and extend a leg, it's thanks to this sense that you know exactly where your leg is. To go for a run, then, or work out in the gym, and not fall or injure yourself, you need a good sense of proprioception. Our sedentary lifestyles are a threat to this sense (and the Covid-19 lockdowns certainly did not help). But climbing trees, walking along balance beams, navigating obstacles, crossing stepping stones (which you can simulate at home, using small mats placed on the floor) are all proprioceptively demanding, and so train this sense. According to research led by a team at the University at North Florida, these kinds of exercises not only improve physical coordination but also working memory.

Yoko Ichino, the ballet mistress at Northern Ballet, based in Leeds, teaches regular proprioception classes, during which students are required to practise complex moves with their eyes shut. "We use our eyes too much," Ichino says. "We need to use all our other senses as well but because our eyes are open all the time, we never develop them. So I put that into my own training." She recommends (if it is safe) to move around your home with your eyes closed. This will train not only proprioception but another suite of senses:

Vestibular senses

Our vestibular system allows us to sense the direction of gravity (and so which way is up), as well as horizontal and vertical movement (as in a car or a lift) and in three dimensions (as on a rollercoaster). Research shows that a healthy vestibular system is important not only for balance but for our sense of being grounded inside a physical body; in fact, people with vestibular problems are more likely to report out-of-body experiences. They're also more likely to get lost, because a healthy vestibular system is important for a good sense of direction.

For all of us, though, the older we get, the duller all our vestibular responses become. (This becomes noticeable at a population level from the not very grand old age of 40). Specific vestibular rehab training exercises have been developed for people diagnosed with definite vestibular problems. But the rest of us will benefit from dynamic movements that require moving the head, like those involved in climbing a tree or practising tai chi, as well as anything that challenges our balance.

Light-detection

We know that our eyes are not just for seeing. When melanopsin-expressing cells in the retina are exposed to light, they send signals to the master body-clock, in the brain's hypothalamus (without causing us to see a thing). Certain variations in the gene for this protein have been linked to an increased risk of Seasonal Affective Disorder, and stimulating these receptors in the morning with suitable levels of light helps to ward off low mood. To improve psychological wellbeing, you don't need to train these receptors to work better, but you do need to help them to work for you by getting outdoors in the morning and avoiding bright light in the evening.

Smell

Smell is not hugely regarded, or developed, in many people in Western cultures. But research with hunter-gatherer groups, such as the Jahai, who live in the tropical rainforest in Malaysia, shows that we have the biological capacity to smell extraordinarily well. Asifa Majid, now at the University of York, and colleagues, found, for example, that the Jahai took on average only two seconds to precisely describe an odour, while Dutch-speakers took an average of 13 seconds to arrive at a much poorer description (describing the scent of a lemon simply as "lemony", say, rather than using more abstract descriptions).

To develop your sense of smell, Majid and others advocate consciously smelling different things, often. Professional perfumer Nadjib Achaibou, who is based in London, tells me that his sensitive nose is absolutely trained, not born. The best way to enhance your sense of smell is to use it, and explore it, he argues: "You might say, 'Oh, I like pepper.' Why? Why do I like it? What is it adding to your dish? That's the first step to enhance your sense of smell. If you see a rose, stop and smell it. If you have a friend wearing perfume, smell the perfume and describe it. When you buy a shower gel, a toilet detergent or a perfume, ask questions. Read the marketing materials, but also trust yourself. You might think, yes they say there is rose in that but what I can smell is lemon. But what kind of lemon?"

Put in the effort to enhance your sense of smell, and you should enjoy all kinds of other benefits. Research shows that a fishy smell improves our critical thinking, for example, while a 2018 study in Germany found that people who are more sensitive to smells enjoyed sex more, and women with a better sense of smell reported more orgasms. "The perception of body odours such as vaginal fluids, sperm and sweat seems to enrich the sexual experience," by increasing sexual arousal, they wrote.

Temperature

We have receptors in our skin that register temperatures within specific ranges. Stimulation of our "warmth-sensors", in particular, has been linked to feeling less lonely, and also "warmer" towards other people. Some of the most-publicised results in this field have failed to replicate, leading critics to question them. However, a 2019 study in Social Psychology suggested that results might have been mixed because researchers weren't taking into account the ambient temperature outside, or inside the lab. When they did this in their research — which involved strapping heated backwraps to participants and asking them about their social plans — the team found support for the idea that feeling cold physically is associated with feeling "colder" socially, driving a desire for more contact with other people. Providing heat (via the backwrap, in this case) could eliminate this effect. 

Inner sensing (interoception)

About 10% of us are really good at sensing our own heartbeat without feeling for a pulse, 5-10% of us are terrible at it, and the rest fall in between. Research shows that people who are better at so-called "cardiac interoception" experience emotions more intensely, enjoy more nuanced emotions, and are better at recognising other people's emotions, which is a critical first step in empathy. In contrast, people who don't experience emotions in the typical way (a condition called "alexithymia", which is thought to affect up to 10% of people, to some extent) suffer from impairments in inner sensing. Could training inner sensing help, then, to improve our emotional wellbeing? It's still early days for this research, but work led by Sarah Garfinkel, now at University College London, suggests that it can. This is a training technique that you could try at home:

1. Sit somewhere quiet and set a timer (on your phone or home digital assistant, perhaps) for one minute, but don't start it yet.
2. Now start the timer, and try to count your heart beats.
3. Do this again, but feel for your pulse this time, to take an accurate measure (this is the feedback that should help your interoceptive awareness to improve).
4. Repeat all the steps.

If you can't sense your heart beating, try exercising first, because this makes it easier.

About the author

Emma Young, (@EmmaELYoung) a staff writer on the BPS Research Digest, is the author of 'Super Senses: The Science of Your 32 Senses and How to Use Them' (John Murray, 2021).