By Doug Linman, PhD
When anyone says how senseless a situation is, or “that was senseless,” or “you are senseless” they are saying that the situation or the person is destitute of, deficient in, or contrary to “sense” as:
1) unconscious - knocked senseless
2) foolish, stupid - certainly
3) meaningless – like a senseless harmful act
So when we are “senseless,” how many areas have been diverted or lost? Well to discover this we must first figure out how many individual senses we might truly have. Then how they are defined by themselves and how are they integrated with other senses to create a system of senses, which of course is my long standing theory that we have a system of senses and not just five.
Some, as far back as Aristotle (384 BC - 322 BC), say we have five “sense organs” These are sight, smell, taste, touch, and hearing. Then around the 1760's, the famous philosopher Immanuel Kant proposed that our knowledge of the outside world depends on our modes of perception. This expression states that each of the five senses consists of organs with specialized cellular structures that have receptors for specific stimuli. These cells have links to the nervous system and thus to the brain. Sensing is done at primitive levels in the cells and integrated into sensations in the nervous system. OK, very understandable! So is it 5 senses tied to 5 sense organs?
Well, let us dig a little deeper.
Some say there are six Human Senses! Sight, hearing, smell, taste and touch are all vital in our abilities to detect outside stimulants, but there are other senses that rely on differing stimuli to help us function. For example, proprioception is the ability to detect the location of muscles, limbs and joints in space, and is considered critical to our ability to operate with ease. Proprioception is what police officers test when they pull someone over and suspect drunkenness. Without proprioception, we'd need to consciously watch our feet to make sure that we stay upright while walking. Although proprioception (or vestibular system for you biologists) may not be classified yet as an official "sixth sense," the other senses would not be as reliable without it. Once again, a system of senses is implied. So, do we now have six senses?
Well let us go a little deeper!
While we can easily identify six senses and related organs quickly, following the basic definition, what about our “skin” and it’s adsorption and absorption self-administering and management properties as a sense? Well the skin does fall within the basic definition of a “sense” and related sensory organs. It has sensory receptors for touch, body temperature, pain, protection, and for determining hot and cold. So, are we now at seven senses!
Generally, human beings can “see,” but that is only the surface understanding. Human vision also entails the ability to distinguish light from dark and even abilities to cross visual frequencies. So our sensory abilities and or system of senses provide further abilities for Humans far above any other animal or species.
Beyond the seven sense organs we have reasonably established, did you know humans have the ability to “echolocate” like bats do?
As any fan of the adventures of the comic book character Daredevil knows, being blind in comic books can give you superpowers. Matt Murdoch was blinded by a radioactive accident and developed a kind of ‘radar’ sense that allowed him to prowl Hell’s Kitchen, rooting out the lowlifes who preferred to lurk in the dark.
Daredevil was built upon the observation that deprivation of one sense can lead to heightened ability in others. Although, this may seem implausible, in fact, researchers have examined a number of blind individuals who seem to have developed extraordinarily acute echolocation, a kind of active sonar that they use by clicking from their mouths or a handheld object to produce echoes from their surroundings.
This “sonar” they use as an especially acute sense of hearing, transforms echoes into spatial perception and image processing! The minds eye if you will. I have a dear old friend who is blind, uses a cane and clicks with his mouth to echolocate. Many times I think he sees far better and more exact than I do, so it truly is extraordinary.
What researchers have found is that blind individuals who could echolocate did not really have better ‘hearing’ at all, but clearly had parts of the brain that were able to extract information from the echoes to spatially observe what was seemingly not accessible to the control subjects who were sighted. Amazing!
So echolocation, or sensing, is broader than perception; that is, our nervous system may react to many things that we are not consciously aware it is handling for us in any meaningful way. Sensing could be ‘bigger’ than consciousness as a sense. So, do you think we are at eight senses now? Well, lets continue because this is exciting!
We, as wonderful and complex human beings have the sense awareness of balance (equilibrioception), pressure, temperature (thermoception), pain (nociception), and motion all of which may involve the coordinated use of multiple sensory organs - back to my system of senses theory.
The sense of balance is maintained by a complex interaction of visual inputs, the proprioceptive sensors which are affected by gravity and stretch sensors found in muscles, skin, and joints, as you can example in basic NASA Astronaut training or SCUBA diving when your body is clearly calling upon other senses to reorient your perception. Disturbances occurring in any part of the balance system sense, or even within the brain's integration of inputs, will cause immediate feeling of unsteadiness and loss of control. Now we are at 9 defined senses.
Kinesthesia is the precise awareness of muscle and joint movement that allows us to coordinate our muscles when we walk, talk, and use our hands. It is the sense of kinesthesia that enables us to touch the tip of our nose with our eyes closed or to know which part of the body we should scratch when we itch, sort of our body’s functional GPS system. Certainly a defined sense for us, which have related sensory organs. So we are up to 10 defined senses now, including our “skin”.
Synesthesia as a possible 11th is a phenomenon in which one type of stimulation evokes the sensation of another. For example, the hearing of a sound may result in the sensation of the visualization of a color, or a shape may be sensed as a smell. This is a new and controversial sense but one that may unfold soon in the science community as falling within the definition guidelines.
It is very possible as well that a “system of senses” will eventually replace the numbering of individual senses because their interrelationship within the human body, as in other species, under standard working conditions, naturally operate as a system.
All presented senses: Vision, Seeing, Hearing, Thinking, Smell, Taste, Touch -Skin Adsorption and Absorption, Balance and Position, Temperature, Ability to Echolocate.
Dr. Linman is our Science Corner writer. He is an engineer and scientist with more than 40 years of experience providing research, interest and insight into these areas.