Imagine looking at an apple. If asked to describe it you would probably begin describing it’s various features: its color, brightness, hue, shape, size, texture, spatial location, etc. Now suppose if someone asked you where are all these features located, you would probably give them a funny look. Isn’t it obvious? Out there! In the apple! They are the apple! That is what an apple is: a conglomeration of various features integrated into one continuous percept. This seems like a perfectly sensible explanation, but if this obstinate person continues his line of questioning and asks you where this apple-percept is located in the brain, you might have to crack open a textbook and get back to him, because now the answer is not so simple.
After studiously pouring over the latest research on visual processing, you are finally ready to give the questioner an answer: no where. Simply put, the various features that make up an “apple” are represented in a highly complicated manner across a dazzlingly diverse array of brain tissue. For the sake of simplicity, brain researcher’s often distinguish between two primary information pathways that sensory data takes: the what and where streams. These two streams form the basis of an exemplary conceptual framework for how the brain processes various features of the objects around us to form a more-or-less continuous percept of objects such as apples. It is these continuous percepts that allows us to manipulate and verbally describe them accurately.
So, if all these apple-features are neurally processed in a separated fashion, why do they appear to be bound together? One obvious answer is they are bound together for the sake of convenience for the perceiver, otherwise how could a person act in a meaningful way? In order to pick up an apple to eat it, a subject must have a more-or-less continuous perception of all the various apple-features integrated into a single spatio-temporal location. This seems to make sense, but who or what are these high-order representations being convenient for? Why would neurons care if things are bound together or not? Surely, from an evolutionary perspective, where efficiency and survival are involved, doing all this extra processing to bind all these neurally separate features together for some subject seems bizarre. Who is this perceiving subject and why would the brain decide to stop the important business of surviving and begin integrating all these salient features into a continuous perception? There needs to be a perceiver for there to be a perception and in order for there to be a perceiver, there needs to be some sort of integrated perception. It seems as if we are at a chicken-and-egg impasse, thus making the phenomenon of unity perception a problem for students of the mind.
There have been many proposed solutions to the binding problem over the years, but they are beyond the scope of this post, in which I only wanted to outline the problem. Whether or not I will attempt to discuss any of these solutions is yet to be determined as of now, but I wouldn’t be surprised if it was the focus of a forthcoming post. Sorry to leave you hanging!