Processing and making sense of the world

Perceiving the information available to us from our external environment is a complicated process and involves sensing the information that’s available around us, ie collecting this information via our sensory organs—our eyes, ears, nose, taste buds and skin.

This information then has to be converted into neural (electrical) impulses which are then sent to the brain. However, this process is only the first step in perception and doesn’t by itself allow us to perceive the world around us in a useful manner. In order for this information to become meaningful to us, we need to make sense of this incoming information, a process which happens within the brain itself.

So do we perceive things with our brain rather than our sensory organs?

In one way, it’s more accurate to say that we perceive with our brain rather than our sensory organs. Let’s take sight as an example—imagine that a wasp is flying past you. Light enters your eye through the pupil (the black hole in the centre of the eye). The lens in your eye then focuses this light onto the retina at the back of the eye. The retina contains millions and millions of photoreceptors which convert light into electrical impulses, which then travel to the brain via the optic nerve. However, this process is only the starting point in ‘seeing’ the wasp. The brain then has to interpret what it is seeing, make sense of it and act accordingly.

This may involve a number of processes such as looking at the constituent parts of the object (ie wings, legs, furry yellow and black striped body), putting this information together, making use of prior knowledge to come up with a name for the object, and then making use of this information to guide behaviour (eg moving away if you are scared or have an allergy to wasp stings). The argument that we see with our brain rather than our eyes, is further supported by the fact that two people may see exactly the same stimuli and yet perceive it differently, or even see things in our ‘mind’s eye’ which aren’t physically there.

You can have a go at doing this yourself—try and conjure up a beautiful beach, or a sunset or even a pink elephant when your eyes are shut. Most people will be able to ‘see’ these things, even when they aren’t physically in front of us and our eyes aren’t open. Try to think about the last dream that you had. Could you ‘see’ things in it while your eyes were actually shut? What could you see?

What might this tell us about the role of the eyes and brain in seeing?