Beyond the Five Senses – Part 2 The Senses

Today we look at our five “main” senses – what we now know about them, what other senses there are and why these other senses are important too. To see the last post which introduced this look at our senses, click here.

It is easy to think of our senses as five discrete ways our bodies perceive information about the world around us. We use our eyes, ears, nose, mouth and fingertips to give us the senses of sight, sound, smell, taste and touch. Yet as we learn more about the senses, this is now seen as simplistic.

What do we now know about these senses?

Our understanding of the senses has evolved with modern medicine and science. What do we know about our senses now?

Smell – is very primal and goes straight into the limbic system of the brain, unlike the other senses which are more “evolved”. Simply put, what you smell is processed by the brain before you are aware of it, whereas with other senses you are aware of it then you process it.  It plugs right in to your basic emotions and thinking. So smell can be influential in ways you are not aware. And this makes sense. Smell is about detecting molecules so is at its most basic about chemical sensing which is critical to all organisms. There is some variety in the other senses which help different organisms perceive their surrounding environment – which we discuss below in Other Senses.

Sight – Humans are very sight orientated, but when we look at how other animals use different senses to travel through their world, we can see why sight can be compensated for by other senses. Sight, or perceiving with the eyes, is just one way an animal can detect the world around it and move safely through it. Humans who do not have sight do find ways to use their other senses to compensate.

In recent years, scientists have been able to create artificial eyes. The implant plugs into the optic nerve and the brain finds a way to make sense of the data from this artificial device.

Sound – The human ear translates sound waves into vibration and then into electrical impulses. As with the eye, there are now artificial devices which can be fitted to collect the sound data and convert it to electrical impulses. So again we have been able to use our understanding of the ear as an input device to create artificial replacements.

In addition to collecting sound information, the ear also provides the sense of equilibrium, important for balance. Whilst also “housed” in the ear, this is now seen as a separate sense (see below), showing the breaking down of the body part = one sense adage.

Touch – touch is the most diverse given it involves the skin on the whole body as opposed to the other senses which are concentrated in specific body elements. Touch can involve pressure, temperature, pain, vibration and other sensations which help us perceive the world around us and also act in it. Touch between humans is also recognised as critical to emotional well-being. Tactile sensations have also been shown to impact on quality of cognition and emotion. Touching textured materials can improve cognition, hep understand abstract concepts and evoke better emotional intelligence.

Taste – Taste receptors are more simple than we think – we tend to attribute the experience of eating with taste. But much of what we think about as taste is actually detected by our sense of smell. As food is consumed the odour enters our nasal olfactory receptors and our brain takes information from both smell and taste to create the rich experience of tasting food.

Visual perception of food also plays a big part. The appearance and colour of food influences the taste you experience. The brain also delivers a taste experience in accordance with how it has been conditioned. We all know the bad experience of tasting something which differs to what you were expecting. It looked like one thing, but was actually something quite different. Even if you normally like the taste, it is jarring when what you are eating does not match the expectation your brain had created.

We also now know that taste receptors are not just located in the mouth. Taste receptors are located all through the digestive system and assist the body in applying the right process e.g. taste receptors in the intestine allow the body to detect sugar so the pancreas releases insulin. These taste receptors in your intestines are no different to those on your tongue. Taste receptors are tuned to ensuring your body reacts to food in the right way. It gives your body information so it can balance core aspects of your body such as salt, sugar, hydration. Most of what you think of as the taste of food is actually the smell of food and the conditioning of your brain.

The most important message however is that we no longer see the senses as five discrete things. They are no longer studied separately. We know there is a lot of overlap such as how much smell influences taste. Much of this overlap is due to the role of the brain at the last stage of all these sensory input channels.

For neurologists, they understand that all these channels are just inputs of data to the brain. Like we saw in the TED talk linked in the first post, the brain uses all the available information to perceive the situation. The brain can use these input channels with some flexibility to create the insights it needs.

Essentially most of our perceptions are multi-sensory in nature. And these sensory inputs influence each other. Input is constantly blended.

So what other senses are there?

Scientists seem to agree that there are now more than 5 senses however haven’t quite decided on how many more there are. Since it all comes down to definitions, different sensory systems can overlap so it is hard to be definitive.

Hearing, Sight, Smell, Touch, Taste – these are easy as they are paired with a unique body part. These are now viewed as the “simple answer” for younger children.

What is the “grown up” answer? Older children and adults are now taught the Nine Primary Human Senses – sight, hearing, smell, taste, touch, balance, temperature, pain, position. There are two senses that humans don’t have which provide the Eleven Animal Senses. The two extras include magnetic sense of direction and perception of electrical fields in salt water. But there are lots of different theories and versions of the list.

Why the variety? Well it depends how you define a sense.

  • One theory is to look at where the input come from. There are a number of types of information about the world an organism can collect: light, soundwaves, odours/flavour, contact, heat/cold, gravity and acceleration, magnetic fields, electrical fields.
  • Another theory is to group them by the parts or systems within our bodies which interact with those inputs. As we saw above, senses don’t equate to a single body part. Our bodies are interrelated systems so it is hard to form arbitrary divides.
  • Yet another way to categorise is whether it deals with internal regulation of the body vs the world outside of our bodies. So maintaining body temperature would be internal body regulation whereas detecting when your hand touches a hot pot handle would be a sense – thermoception. Of course body regulation happens in a context of temperature of the environment so again it is hard to find tidy divides. We need to sense the external environment for the body to compensate its regulation for those conditions.

Possible ‘extra’ senses to be aware of include:

  • Proprioception – sense of your body in space. Understanding the position of your limbs and muscles without looking. For example being able to move your body with your eyes closed to either clap or touch your finger to your nose.
  • Equilibrioception – sense of balance such as when walking along a narrow surface
  • Linaesthesia –  a sense of movement
  • Thermoception – knowing if the environment around you is hot or cold.
  • Nociception – ability to feel pain
  • Chronoception – sense of the passing of time

Senses humans don’t have include:

  • Electroception – some aquatic animals can sense electrical fields, specifically change or disturbance in electrical fields. Examples include sharks, dolphins and sting rays. This sense is useful when the animal is in murky water or it is detecting prey in the silty seabed. This sense only works in water, but the equivalent for non-aquatic environments is static charge which a human can get on occasion.
  • Magnetoreception – some animals can detect the earth’s magnetic field and use it powerfully for navigation. This helps birds migrate and bats navigate at night.

Next Time

Next time we will look at the third post in the series – the importance of sensory engagement. This will be more focused on our professional work in managing our environment.

The full set of posts for this topic are:

  • Understand what a sense is and why senses are important, including to a person’s mental and physical well-being (click here)
  • Look at what we now know about the five main senses and what other senses there are and why they might matter (today’s post)
  • The importance of sensory engagement for people in the urban environment, particularly for children and their development
  • How understanding your senses can help you deal with technology in a digital world

 

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