More than 5 senses

I grew up learning that there are five senses: sight, smell, hearing, taste and touch. My eyesight has always been less than perfect, so I learned from an early age to have my eyes tested, fitted with glasses and my vision corrected. For many years I wore contact lenses under the belief that the lenses were slowing the progress of a degenerative condition. When the discomfort associated with wearing the lenses became intense, I took a break from the contacts and discovered that they were not helping. Since, I’ve been able to wear glasses comfortably and achieve vision correction. So I understand vision and regular testing and measuring of that sense. In a similar way, I know about hearing testing. I’ve had a basic hearing test and so far I haven’t had problems with my hearing. I have also heard that there are some tests that can measure smell. A smell test is often administered as part of the diagnosis of certain types of dementia. I am less aware of the tests that can be done to measure taste and touch.

Studies aimed at understanding and helping children and adults who have trouble with sensory processing have led scientists to posit two additional senses. And, being scientists, they have assigned names that are more difficult to remember than the names of the first five senses.

The sixth sense is called proprioception. We all have receptors in our muscles that tell us where our body parts are. These receptors work in conjunction with our brains to give us real time information. We don’t have to look at our hands, for example, to know where they are. This sense enables me to use my keyboard while my eyes are on the screen of my computer. My fingers go to the appropriate keys without my needing a visual clue as to their location. This system, however, is less functional in certain conditions. We have a son who experienced a small stroke during birth. The tiny area of his brain that is affected is barely visible on a CT scan, but the result is that he has diminished proprioception of his right hand and arm. Physical and occupational therapy combined with years of careful practice have given him use of that hand and arm, but he is extremely left-handed. His right hand and arm work mostly as helpers for his left hand and arm. This has very little effect on his ability to us tools and do his life’s work, but as a child he was sometimes identified as uncoordinated or clumsy, when what was really going on was diminished proprioception. Children with more severe sensory processing issues become afraid of certain physical activities and require additional help to engage in normal activities.

The seventh sense carries the name vestibular sense. The vestibular system includes the parts of the inner ear and brain that help control balance, eye movement and spatial orientation. It helps keep you stable and upright. Those experiencing vestibular issues may not know where their body is in space. They feel out of balance and out of control. A friend, after experiencing a stroke, has experienced severe vestibular issues. When his body is leaning to the right, he senses that it is leaning the opposite direction. His natural motions to correct result in his tipping over. Months and months of physical therapy have enabled him to make great progress and he can now walk short distances with a walker and is able to sit upright in a normal chair, but his mobility is severely restricted and he ends up using a wheelchair for mobility most of the time. It is unclear how much function he will regain.

Our senses don’t stop at seven, however. There is an eighth sense that also gets a modern, scientific name. Interoception is the ability to know what is going on inside your body. Issues with interoception usually show up in childhood. Kids who struggle with interoceptive sense may have trouble knowing when they feel hungry, full, hot, cold or thirsty. It is thought that interoception is similar to proprioception. Just as receptors work in conjunction with the brain to tell muscle and joint positions and the location of body parts, receptors inside organs send information about our bodies to our brains. Vital functions like body temperature, hunger, and thirst are immediately obvious to most of us. Less obvious are receptors that give information about digestion, respiration and heart rate. Most of us are fairly good at knowing when we are out of breath or struggling to gain our breath after intense physical activity. It is pretty easy to count our respiration rate. We also have rudimentary awareness of our digestion system. We know when it is time to use the bathroom, for example. Awareness of heart rate is a bit of a challenge for many of us. However, since being diagnosed with an occasional irregular heartbeat I have trained myself to have increased awareness of my heart. I can sense when it is beating faster or slower more easily than was the case for the many years that I completely ignored my heart.

Experts studying interoception believe that mindfulness activities such as meditation can help with learning to be more aware of interoceptive sensations. Studies conducted with Buddhist monks have shown an amazing level of awareness of and control of heart rate, for example.

Like the 5 senses, the three additional ones have a degree of learning associated with them. Just as we can learn to look for certain things, we can learn to sense certain activities within our bodies. With my vision issues, I had to learn to look for wild game on distant hillsides, for example. Once I understood that I was looking for motion more than for color contrast, I became better at spotting game. A similar learning took place for me in the development of fishing skills. I had to learn what to look for. We can train our listening to be more sensitive to the sound of our children’s voices or to certain warning signals. Practice improves our senses of taste and touch as well.

Knowing about and practicing skills of proprioception, vestibular and interoceptive senses can help us understand ourselves and others better.

Copyright (c) 2018 by Ted E. Huffman. I wrote this. If you would like to share it, please direct your friends to my web site. If you'd like permission to copy, please send me an email. Thanks!