Dr. Lisa Feldman Barrett, a neuroscientist, looks into the different ways we can understand the world that go beyond what we see, hear, touch, taste, and smell.
What is the normal number of senses a person has? If you think of senses as their receptors, like the retinas in your eyes and the cochlea in your ears, then the standard answer to this question is five: sight, sound, touch, smell, and taste.
They are called “extroceptive” senses because they tell us about the outside world.
But your body also has receptors for things going on inside of you that you don’t even know about, like your heart beating, your lungs growing, your stomach gurgling, and many other things. They are often thought of as a single sense, called “interoception.”
However, the appropriate response to this issue is even more involved and intriguing to consider. For one thing, your body possesses receptors that are responsible for carrying other forms of information, such as temperature, which are not typically considered to be senses by most people.
In addition, some of your receptors serve more than one purpose at the same time. Some of the cells in your retina may communicate with your brain to let it know whether it is daytime or nighttime. For example, your retinas are gateways for the light waves that are necessary for your eyesight. This nameless ‘day/night sense’ is the basis for circadian rhythms, which influence both your sleep/wake cycle as well as your metabolic rate.
Even those senses that appear to be the most essential, such as vision, are inextricably linked to other senses that appear to be distinct from one another.
It has been discovered, for instance, that what you see and how you view it are linked to the way in which your brain monitors your heartbeat, which is an aspect of the sense of interoception.
Your brain takes in less visual information from the outside world whenever your heart is contracting and forcing blood through your arteries. This happens because your heart is working harder.
In addition, your brain creates senses for which you do not have corresponding receptors. Examples of this include flavor, which the brain creates by combining data from the senses of taste and smell, and wetness, which is formed by combining data from the senses of touch and temperature.
In point of fact, your brain produces everything that you see, hear, smell, taste, and feel by drawing on information from a wider variety of sources than just the receptors on your body’s surface. To give one simple example, light waves do not simply enter your eyes, proceed to your brain as electrical signals, and then cause you to see something.
Your brain actually makes predictions about what you might see before you actually see it, taking into account your previous experiences, the state of your body, and the circumstances of the present moment. It does this by combining its own predictions with the sense data that is coming in from your retinas to create the visual experience that you have of the world around you.
When you place your fingers on your wrist to feel your pulse, for example, you are actually perceiving a structure that is based on your brain’s predictions as well as the actual data that it is receiving from your senses. Your sensory organs do not allow you to feel sensations in any way. Your thoughts are what give you the experience of things.
