In which the reader examines the management of language within her cerebral cortex and meets mental lexicons there; is introduced to top-down and bottom-up processing, cascading feature analysis and parallel distributed processing. She also goes to a party and considers a dog.
We will be discussing the nitty-gritty of language management and its implications for literacy a little later. Finally, we will find ourselves at an elderly, but still fundamental, controversy which we can then fruitfully examine in the light of the above. We start, though, with a little fundamental neuroanatomy and neuro-psychology. Where, and how, do procedures relevant to literacy actually happen in the brain?
Our cerebral cortices, one left cortex and one right cortex, where we think most of our ‘thinking’ goes on, are very swift and have huge capacity. The details of their procedures, however, remain imperfectly understood, to say the least. All the same, we know that certain fairly specific areas of our brain are involved in certain fairly specific functions of our minds. We know, for example, that most people manage language pretty well exclusively in the left brain, and we know roughly where we do this. The basic neuroanatomy of language management in the left brain is pictured at figure 2.1 in outline and is immediately explained in the text. Later on, and bit by bit, this anatomical mapping will be lined up with logical and empirical cognitive mapping of literacy management. Anatomy will be shown to fit logical deduction and empirical findings. (The complete proposed map of language management is at appendix one if you need an early peep.) As a result of this marriage of observation with logic we will be able to see how and where those literacy procedures we reliably observe or infer, from real life and from experiments, probably happen in real brains. We need to understand all this if we are to consider the issues still being fought over as to how we really manage literacy and so how best we should present it for learning. It is important that we bear in mind that what follows is simplified. It is, nonetheless, close enough to the probable truth to enable valid and valuable insights into literacy to be found and evidence-based, practically and pedagogically useful conclusions to be reached.
Imagine you are chatting with someone. Using the outline of language management centres and pathways at figure 2.1 below, let us consider how you might be translating the noises your companion is making into meaning inside your head. You will necessarily have to consult a language store, or lexicon, of some kind to do this. You will have to consult a mental lexicon, so there must be one in your head. Mental lexicons will reappear when we examine routes to reading and routes to spelling. But where is meaning and what is it? What is a mental lexicon? What will it contain? How might it work? Is one lexicon enough?
A lexicon is a store of language. One form of mental lexicon might be a dictionary of word meanings in your head, but what other forms might a lexicon take? Is there just one, with every word you know filed under its meaning, perhaps in sections of related meanings or with a quick-find system of extensive cross-referencing by meaning? You certainly have a large vocabulary with a huge number of entries and an extraordinarily rapid access system. You probably have entries for somewhere in the region of 50,000 (that’s fifty thousand) items, and you can reach any one of these entries in less than a second (Aitchison 1987). And, of course, you may be able to match this several times over, in different languages. (Remember how colossal your brain is and enjoy it!)
But there is more. We deal with language in several other, and completely different, manifestations. We hear it as sound. We see language as symbols, as you are doing now. We understand language as abstract meaning (unrelated to sound or symbol). We also manage it as sets of detailed motor instructions to muscles (the muscles dedicated to producing speech or writing). It follows that we must have sites in the brain where all these utterly different incarnations of language are stored and where they can be accessed for the purposes recognition (reading or understanding speech) or execution (talking, writing or thinking). These sites are also mental lexicons.