I see!

Cognitive psychology is often introduced by asking questions like: “How do we perceive the objects in our environment?” This question is then translated in slightly more technical terms as: “How does the brain create a meaningful picture on the basis of the light-rays that stimulate our retina?” The process that makes makes pictures from light-rays is called the process of visual perception. Instead of discussing the various theories that try to explain what the mechanism behind this process might be, I would like to question the question itself.

In my view, the question itself is seriously flawed, based on three errors of thought. I will call these errors the observer-error, the system error and the metaphorical error. (But perhaps better names can be found, or have been found, for each of the errors, elsewhere, since I have not made the effort of doing a literature search on this topic).

The observer error
The first thing to note about asking questions like the one above is that it involves asking after the explanation of something that might not even exist in the first place. We ask: How do we create meaningful pictures in our head? Well, perhaps we don’t create such pictures, so the entire question becomes empty. Let’s think about the question from this point of view and try to analyse how we come to take for granted that ‘making a picture in your head’ is a valid starting point for investigation. I seem to know that I create pictures in my head (Hey, I do see, right?). But how do I know that you create these meaningful pictures? For an intuitive observer, it might seem to be a clear fact that human beings create a picture of the world inside their heads. But there is no observable evidence for this on the outside. Note that all research on visual perception is *based* on first asking the above question. The fact that visual perception is some kind of information processing mechanism that should produce, as output, *a picture* (an image, a pattern, "the thing that we see", or what have you), is taken for granted. It is a starting point. This means that the further empirical evidence coming from research on visual perception cannot be counted as evidence for the existence of the phenomenon-to-be-explained. The evidence merely has something to say on the question of what the mechanism for visual perception is, *assuming* that it is something that will produce a "picture" in our heads.

Now why is it so difficult to believe that we are *not* creating pictures in our head? Well, this has to do with the fact that researchers are always human beings, and we, ourselves, are in the business of visual perception, and we are consciously aware of this ‘fact’. The personal reflection of how visual perception *is experienced* by us confounds with the scientific, observable definition of the phenomenon that needs to be explained. Now, there is nothing wrong with taking a conscious experience as a phenomenon to be explained, but we should be clear about the status of the phenomenon. So what we should ask instead is: How is the conscious experience of a meaningful, visual, picture of the world created? This is a different question. All options are open. We could, for instance, claim that the meaningful picture is just an illusion of our consciousness and that the sensory input on our retina does nothing to create such a picture in reality. We dream our way through life, one could say. We could also claim that the visual input is causing coherent pictures to arise in consciousness, but that this is not very *interesting*, because the function of visual input is mainly to directly constrain behavioral output, and that the coherent pictures and patterns, i.e., the "seeing" that we experience, is only an after-effect, a side-issue.

Whatever the answer, the observer-error states that we should not confound our personal experience of the phenomenon with the scientific (observable) definition of the phenomenon. In the scientific definition, all we have is either a physical process (light falling on the retina), or a conscious living being *reporting* that he "sees things". There is an intuitive, but dangerous habit of automatically assuming some information-processing device (a ‘machine’ that processes the light on our retina to produce the consciously experienced picture in our head) which is posed in between the physical and the conscious phenomenal levels. But this device is not a real phenomenon at all, it is a theory in itself, and it is a theory that could be false.

The system error
This has to with time, and with the assumption on the direction of the flow of events in the phenomenon to be explained. When we ask: how does the light on our retina get to be transformed into a meaningful picture of the world?, it is automatically assumed that *first* there is light on the retina, only after which this light is transformed, step by step, into a meaningful picture. The flow of events, through time, is linear (sequential, procedural), starting with the light out in the world (what is sometimes called one of the 'sensory qualities'), and ending with the conscious visual experience. The metaphorical comparison with a machine that receives input and produces output, going through a series of sequential steps is easily made. This picture of process flow is ubiquitous in college textbook explanations of the structure and processes in the brain. It is how I tell it to my students: Light hits a dog, reflects, hits our retina, excites nerve cells, which excite further nerve cells, which sets in motion a train of nerve impulses that travel from the eye into the optic chiasm, into the lower brain areas, into the cortex, starting in V1, splitting up into the dorsal (on the top of your head) "where system" (where is the dog) and into the ventral (on both sides of your head) "what system" (it's a dog!). Upstream, somehow all visual information gets to be "integrated", producing a coherent picture of a dog. Then you get to shout "hey, it's a dog over there", or something like that. But this picture is a charicature of what is really happening, and I’ll tell you why.

For starters, in the brain, activity runs in more than one direction, since every nerve cell is heavily connected with both feedforward as well as feedback connections. So, no matter which nerve-cell in the ‘stream’ we take as a starting point, activity is then spread both upwards and downwards, at the same time. It is one thing to acknowledge the fact that parallel processing takes place in a system (as everybody does), it is another thing to really think through the causal consequences. Consider that the phenomenon of me observing a dog takes some time in itself. I see something that will turn out to ‘be’ a dog, I continue to look at it, and in the continuous process of seeing this thing I see more and more of the dog. I might at first see that it is a brown living animal, even before I see it is a dog. But seeing that it is a brown living animal suggests that the complete visual stream is already activated (producing the brown living animal experience, right?). But that means that before we actually recognize the dog as a dog, massively parallel processing is going on. So even before we ‘recognize’ a dog being a dog, thousands and thousands of neural impulses are already shooting upwards and downwards all over the system. So what does it then mean to say that we “process the sensory input and thereby recognize the dog”? It means nothing, because the recognition of the dog might just as well be attributed to the feedback activity from the cortex back to the eye, instead of the activity that goes from the eye to the cortex. We might even consider the possibility that the observer just wanted to see the dog, which sort of places the causal origin of the perception of the dog completely inside the observers head. The whole process didn’t start with light falling on the dog at all, it started with my own mental activity!

I do not wish to claim that visual perception is a kind of dreaming that has nothing to do with what happens outside of us. But what I want to conclude here is that visual perception is not, at least not necessarily, a sequential process that starts out there and ends in here. In the brain, multiple parallel processes run upwards, downwards and sideways in a massively connected network. What gross simplification to tell our students that recognition of a dog is a five step procedure that hops from the eye to the temporal lobe and that’s all there is to it?

The metaphorical error
I will try to be quick about this one because my space is running out here. The metaphorical error is related to the errors above. It encompasses the above ones, I guess. It refers to the idea that in asking the question: “How does our brain create a meaningfull picture on the basis of visual input?”, we automatically, implicitly, apply a metaphor to human cognition that might be false. The metaphor is of course the metaphor of the information-processing machine. A real, physical machine that is, in the strong sense, comparable to other mechanical devices such as telephone-communication systems, bicycles, trains, and computers. (So I do not mean a machine in the general sense, in which all processes are by definition ‘machines’). If visual perception is a process that is executed by a machine, then this automatically necessary that this machine have some input, and what better input to take than the light that reflects on the retina? And if this machine is to have some output, than what better candidate might there be than our ‘visual thoughts’, the visual experiences we have when we look, see, observe the world out there? But there is no proof whatsoever that visual perception is such a machine, or explained by such a machine. In fact, it is a non-machine in the first place, since it has physical stuff as input and meaningfull information as output. Such a machine cannot exist. The metaphor is a smoke curtain that obscures the fact that between light on our retina an meaningfull pictures in our head lies a complete mind-body problem (how to get from stuff to ideas), a problem that has not been solved. You cannot just imagine a machine to solve that problem, the problem is fundamental. We probably need a completely different conception of cognition in general in order to solve it.

Ok

So, Jelle, if this is all wrong then, what is your own idea, what is visual perception if it is not the machine you just discarded?

Well, I don’t know, of course. But I do have some hints, some questions to ask. I will pose them here as my final thoughts:

• What comes first, seeing, or acting? When I move my eye, is that considered to be a response, or the active search for a new stimulus?
• What is the goal, the utility, of visual perception? Surely a device so complex as the visual system (the physical stuff that is, eye, brain, and so on) did not evolve in order to create pictures inside our head. Could it be that the adaptive value of visual perception has more to do with sustaining a satisfactory relation with our environment, instead of just seeing the environment?
• Is there really a difference between the inner eye (imagination/dreaming, and so on) and ‘real seeing’? Or is the perceived difference between the two phenomena itself an illusion we create ourselves?
• Who is doing the seeing? We automatically ask: How do people... (follows some cognitive function). But what is this ‘people’ we speak of? Is it my brain that sees? Is it the person Jelle? Is it the Jelle that other people speak about in their native language? Is it the Jelle you just imagined writing this short essay? As long as we haven’t solved the problem of what a human being is (and at which explanatorial level(s) he ‘exists’), how can we answer such a question?
• Should we explain behavior, or the mind? Is the mind really a phenomenon, or is it already in itself a theory (as Churchland would have it) that might be false?

Although I didn’t set out to end up where I do now, all these questions seem to run directly towards the good old mind-body problem again. Time to stop, I guess! If you want to read more about this famous problem in philosophy, you can do it here. See you next time!