We only have our own unique window looking at the worlds so how do we know what’s really going on out there?
It’s funny to think that we’re looking at the world through a window, but that’s a fairly apt analogy. The five major senses that we use to experience our surroundings, sight, hearing, touch, taste and smell, have given us everything we know about the world around us. But do they limit the kind and amount of information we can perceive?
We humans see only a limited band of the electromagnetic spectrum, but some animals and insects can see ultraviolet light or infrared which is invisible to us. Our ears can’t pick up the sound of a bats high pitched voice that it uses to sense its prey and surroundings with echolocation. What can enter our consciousness is limited by what we can sense. What seems like everything to us is actually only a small slice of what’s out there.
On top of our senses limiting what experiences are available to us, our brains too limit how that sensory information is experienced. It does this by making informed guesses about sensory data and filling in the blanks for us. One quick example is the blind spot in our visual field, which is created by a lack of photoreceptors where the optic nerve exits the eye. There are simple experiments you can do to experience it for yourself. However we never notice this blind spot because our brains fill in the missing visual information.
In addition to filling in holes in our sensory experience our brains also delete, or exclude from our primary awareness, much of our sensory experience. This is easily demonstrated by staring at a single point in a scene for thirty seconds and then looking at a blank wall. The inverse image of what was in the scene floats in your visual field. Our brain tunes out the static imagery, which makes moving things stand out much more.
In fact a lot of what our brains do is manage our perception. it is our complex brains that give us this ability to interpret an avalanche of sensory information and determine what deserves our attention and what can be ignored. But maybe we need to back up a bit.
Let me return to my definition of consciousness as the capacity to have an experience. With that basic definition it becomes clear that a definition of experience is necessary. When we human beings have experiences they are hugely complex multi-sensory happenings that include our senses and thoughts. So it’s helpful to differentiate the parts of ones experience. In neuroscience experiences are divided into sensation and perception. Sensation is where the nerves originate the signal sent to the brain. Perception occurs when that signal reaches the brain and is interpreted. Vibrations in the air moving cilia at the end of nerve cells in your ear is sensation. The bark of a dog is the perception.
So with that distinction, what kind of organisms can actually experience the world? If our experience is both the sensation and perception, the experience starts with the sensation and ends with our perception of the sensation. The perception is our brains making sense of the sensation. So is a brain necessary to perceive sensation?
Tiny single celled organisms like bacteria can move around, find and move towards food, and avoid harmful substances. They are sensing their surroundings and reacting. Slime molds are even more resourceful, and have been shown to be able to figure out the way through a maze by extending a network of branching tubes in search of nutrients. When it finds a food source the branches on errant paths retract to focus its energies towards the food source. It’s not seeing or thinking, but sensing it’s way. It’s easy to imagine they have some feeling of what it is like to be that organism, with the discovery and sensation of food provoking an interior experience, but these simple organisms are not perceiving the world; they’re not making sense of their sensations.
We can observe, with our senses, a self organizing collection of molecules metabolizing and reproducing, moving trough its environment, an seeming to behave in an intelligent way. Does this mean that simple organism is having an experience? It has no nervous system to process stimuli. But does it need one?
What is sensation anyway? We experience the world through our limited sensory modes. So what are we really experiencing? What is happening when we touch the soft fur of our cat? When we smell breakfast being made? Or when we open our eyes in the morning and catch the first rays of sunlight through our window?
What we take for granted, our own personal experience of the world, is actually quite mysterious. So how do we know what we sensing and perceiving?
On Mind and Matter 