It is said that our eyes are the windows to our souls. Well, wherever you stand on the existence of a soul, the eyes are definitely the windows into the mind. Along with the ears and all our other senses. There is no way for us to interact and learn anything from our world if we don’t perceive it. . We detect our external environment by decoding the light we see – how it’s absorbed, how it’s reflected off surfaces and edges, how much of it there is and how these things interact and change.
Our vision is basically the interpretation of light, everything we see is light, and that includes colour. There is no such thing as colour technically – we have different cone cells which process different wavelengths of light and it is this which our brain interprets as being colour, but colour itself is a construct of your mind. Mind-bending, but true. The light in your world is turned into electrical activity by the cells in your eyes and your brain converts these signals into meaningful patterns and stimuli in your environment. We see what our brain decodes and processes – that is very much not everything.
Next time you look at a person’s face, try to think about how the different amounts of light are being reflected from the contours of their faces, eyes, noses, skin and hair. These different aspects of a face absorb and reflect light differently and it is these differences that your eyes are translating into electrical activity, and your brain is deciphering this code and translating it into a picture of that person.
And we don’t all do this in the same way. The basics are technically the same, but some people are unable to see the same as the rest of us due to not having the right numbers of cone cells (colour blindness) or a problem with a particular processing pathway (for example visual neglect where patients are unable to process one side of space), or even a problem with the visual cortex itself (for example if the bit of your visual cortex which processed motion is damaged, V5, then this is called akinetopsia and you can’t perceive motion – a bit like permanently living with a strobe light on, incredibly disorienting). In these cases lives are affected to differing degrees and the overt behaviour displayed is modified as a result.
Your behaviour potentially changes in relation to what you perceive. For example if you can’t perceive colour properly you cannot be a pilot or an electrician, but you can still drive because there are other cues (the order of the lights) which are non-colour dependent that can be used instead of the usual colour cues. Behaviour may be limited by differences in perceptual abilities, but it isn’t necessarily prevented entirely.
The processing of the light detected by our eyes is sent on 2 pathways, the ventral and dorsal routes, or our ‘what’ and ‘where’ pathways. The dorsal (where) pathway goes through our parietal cortex. This is the area of the brain which is heavily involved in our attention processing and decision making– we need to know where something is quickly so we can get out of the way if it’s moving towards us (for example a sabre tooth tiger – well you never know) or scoop it up if it’s a toddler wanting a cuddle. Plus we need to know how to move around stationary objects like a tree or a parked car so we don’t look like a complete loon walking into the doorframe. Where something is typically is more important than knowing what something is, so we process this bit first.
But we can only interact with objects such a shock generators [as in Milgram’s famous study] if we know where they are. We can only identify objects and work out how to interact with our world if we know what the objects are and how they are used. So we have evolved what is known as the ventral (what), pathway to process objects: this is the pathway that goes through the temporal lobe, which deals with pattern recognition among other things.
So our perceptual pathways work together to process the light in our environment to enable us to interact with our environment and flick switches on a machine that gives people electric shocks, get out of the way of a sabre tooth tiger, or comfort a friend or toddler if they’re crying. Lovely. But we can’t process everything in our environment, or out brains would be the size of football pitches, or at least ridiculously big. So we have this thing called attention, which decides what is or isn’t important to process.
If we don’t attend to something we aren’t aware of it. The reality we are aware of is a combination of our focus of attention, our perceptions and how our brain combines them. If we don’t attend to the shock generator [like in Milgram’s experiment] we are unable to flick switches and would ruin the experiment, if we don’t attend to our friend while they’re talking we won’t hear what has happened and will either miss out on gossip or not be able to comprehend why they are upset about something. A phenomena that most may have seen, if not heard of, is inattention blindness. If you are not behaviourally focused on an element of your surroundings then you are not attending to it and it does not get processed – even if that happens to be a big black gorilla waving at you. There are numerous examples of this, the most common is the standard video here, but my favourite is this one here which links in the inattention element with change blindness, which I’ll cover in a moment.
We are literally unaware of some things if we are cued away from that location or events happen between eye movements. Our eye movements are called saccades and they’re basically little jumps between aspects of space – and during the jump we don’t process visual stimuli at all.
Normally this isn’t of consequence, but if something disappears during one of these eye jumps/movements (saccades), we don’t notice, at all. Or if something appears or changes during one of these saccades we don’t always notice, particularly if we’re not focused on that exact area where the object is appearing/moving/changing and so on. If we are not attending to something we are blind to changes that are occurring, this known as change blindness and it means we don’t see the food vanishing from our plate when our date is eating all our chips because we’re so distracted by their wit and charm, or we don’t notice the clues that tell us it’s a trick when Dynamo is doing one of his illusions.
We do however, have control over what we attend to, this is known as selective attention – the selection of one thing over others to process and focus on in order to achieve a behavioural goal. You’ve chosen to read what I’m wittering on about as you see it as relevant for your behavioural goal of learning something about the world of psychology and how humans interact with it.
I’ve mainly covered visual information here as it’s my specialty, the light which hits your eyes and is converted into electrical activity for the brain to interpret. But the other senses work the same way, haptic (touch), auditory (sound), gustatory (taste), olfactory (smell), they all involve external information being translated by the cells in the initial receptors into electrical activity that your brain processes. All of this information, from all your senses, is combined into a picture of the world. The only problem is it’s not complete, because we can’t process everything at once.
One thing your brain does not like is a void, gaps are logically not valid, so the brain extrapolates the information and forms a ‘best guess’ hypothesis about what is there. Sometimes it’s pretty accurate – your peripheral vision for example. There are very few cone cells outside the retina, so the bulk of peripheral vision doesn’t actually contain what we perceive as colour. And yet you can all see colour throughout all elements of your visual view at the moment. If you hold your hand out to one side of you, just at the edge of your peripheral vision, it’s still in colour. Your brain is making that assumption though, based on the fact that it has perceived it in colour multiple times previously. But it’s a construct of the mind when it’s in your peripheral vision – you’re not technically processing the light as colour.
This works for motion too – in the absence of directional cues, your brain simply picks a direction and goes with it! The Spinning Dancer is one of my favourite visual illusions – here is the full thing, each side has the directional cues in red/blue, if you look at each side you’ll see that the dancer in the middle (minus directional cues) changes direction. Your brain is incredibly fast to process change.
What you know (called top-down information) combines with what you see (known as bottom up information) to create your experience of the world. The information you receive (the bottom-up information) is incomplete, so you need the prior experiences and knowledge to fill in the gaps (the top down information). Everything you experience very literally impacts on your perception of the world – you interpret this sensory information (for example light or sound) in the context of what you already know.
What you see is very literally what your brain is constructing, your visual experience is a combination of what you perceive and what you already know. So it isn’t real. And it certainly isn’t what somebody else is perceiving at that exact moment in time.
So when you’re not seeing eye-to-eye with someone, cut them (and you) a bit of slack, they may very literally not be perceiving the world in the same way as you are.