Recent research on the human brain has greatly improved our understanding of how we read and write.
Various types of brain scans can allow scientists to see which areas of the brain are active for different functions. And when damage occurs to a certain area of the brain - for example in motor-car accidents - we can learn the function of the damaged area by noting the resultant deficiencies in brain function.
There are several areas of the brain that are used in the processing of language. The "Visual Processing Area" or "Visual Cortex" is at the back of the brain (in the Occipital Lobe).
When we read, information is passed from the Visual Cortex to an area called Wernicke's Area (named after a German neurologist). This area, partly in the upper part of the Temporal Lobe and partly in the Parietal Lobe, is where the visual information seems to be decoded and meaning extracted.
When we are reading aloud, or when we are speaking, information regarding a meaning or concept is sent from Wernicke's Area to Broca's Area (named after a French physician), which is in the lower part of the Frontal Lobe. Broca's Area decodes the meaning or concept into instructions which are conveyed to the Motor Cortex - an area at the top of the Frontal Lobe. Excited nerves connected to the motor area of the brain then control the speech-producing organs in the mouth, face, throat and lungs - or, in the case of writing, to muscles in the fingers and hands.
When we are listening to speech, information generated by the sounds from the ears are sent to the Auditory Cortex and then to Wernicke's Area for the extraction of meaning.
Broca and Wernicke carried out their work in the late 19th Century. The language areas they discovered lie in the left hemisphere of the brain for most people - although for some people (mainly left-handers) the predominant language-processing hemisphere is the right one.
In 1973 John Marshall and Freda Newcombe in Oxford proposed that reading
involves two processes or "pathways" in the brain. One pathway (called the
"phonological", or sound route) works out the sound of the word from the
spelling, and then derives meaning by recognising the sound. The other
pathway (the "semantic", or meaning route) derives the meaning directly by
recognising the pattern of the written word ("look and say"). (See Scientific
American, Oct. 1993)
Fig. 2 shows a proposed model for reading processes in the brain, based on the two-pathway idea but covering the two cases of "reading aloud" and "not reading aloud". (Scientists use the term "model" to describe a theory that they don't really know is correct, but which can be used to explain some of the observed facts).
In this figure the processes in dotted boxes are carried out when reading aloud. They are also carried out to some extent when reading silently - even then we are at least partly aware of the sounds of the words. Children who are learning to read will normally sound out the words to themselves even when reading silently, and adults may do this too at a less conscious level.
In this model, the word-meaning-sound pathway of reading involves a written word-pattern (for example, the word-pattern 'cat') being recognised as being the same as one in our memory (in our storehouse of written words). Then, because that written word in our mind has a link to a meaning (or picture, or concept), we can become conscious of the meaning. We refer to this pathway as the "whole word" route.
When we are reading using the word-sound-meaning pathway, the written word is first broken up in our mind into segments (for example, c-a-t), and these segments are combined to give a mental representation of the sound of the word (for example, the sound 'cat'). This word-sound is then recognised as being the same as a word in our storehouse of word-sounds in our brain. Then, because this stored word-sound is linked to the meaning of the word, we can become aware of the meaning (for example, we may picture a four-legged animal with fur that purrs). We refer to this pathway as the "sound-of-the- letters" route.
Studies have shown that when a word is checked against the storehouse of words in the brain - whether it is a written word or a word-sound - only the main part of the word is checked first, and then the ending is processed separately. For example, 'sing', 'singing' and 'singer' would all be checked against the base word 'sing'.
Proponents of this "two pathway" model consider that, for most adults in most reading situations, the two pathways are complementary and proceed in parallel (together), with meaning being extracted from written words using both methods at once in order to achieve the quickest and most accurate response possible.
The "two pathway" model of reading can be used to explain mistakes that people sometimes make when they are reading. For example, sometimes when a person is reading out loud they will make a mistake and speak a word that is different from the one that is written, while still conveying the correct meaning. For example, they may read "they went to bed", but say "they went to sleep". This shows that they are extracting the meaning before they work out how to express that meaning in words - they are reading using the word- meaning-sound pathway.
On the other hand, we sometimes see a news-reader on TV speaking material that he hasn't quite understood yet - so that he accents the wrong syllables or words, or gives the wrong pronunciation for a word, or even repeats whole phrases. Such a reader is clearly using the word-sound-meaning pathway. With this pathway he works out the sound of the word from the letters of the written word. Then he extracts the meaning of the word, and speaks the word, in parallel - that is, the extraction of the meaning and the speaking processes are carried out at the same time (by different parts of the brain). Such kinds of mistakes do not occur when a person works out the meaning first, then works out the word-sound, and then speaks that sound.
But it must be stressed that at this time (2003) there is very little clear and accurate knowledge about how most brain processes actually work. We do know that a person has about 100 billion brain cells (neurons) in his or her brain, and that memory consists of connections, or networks of connections, between these cells. But there is, for example, little knowledge about how the brain stores the three banks of data required for language processing:
- written words - that is, sequences of symbols or letters which make up meaningful words. Most speakers of English have a storehouse of about 10,000 to 20,000 basic words stored in their brains, plus variations using different endings (for example, -s, -ed, -ing, etc.) and prefixes. The way these words are stored must be extremely efficient and intricate, since we can recognise capital letters ('CAT' as well as 'cat'), big letters as well as little letters, italics as well as straight up letters, etc.
- word-sounds. We know that the brain stores word-sounds - or some kind of representation of them - because we are able to recognise the sound 'cat', for example, when we hear it. How does the brain store word-sounds? Clearly it is not the sounds themselves that are stored - imagine 10,000 sounds buzzing around in your brain! So sounds must be stored in some kind of code - perhaps in a similar way that modern computers store sequences of sounds. We know that information from the ear is transmitted to the brain by means of strings of electrical and chemical data passed along special types of cells. Also that stimuli in the Motor Cortex are transmitted in a similar way to the various organs and muscles that control speech. So perhaps the storage of word-sounds is achieved using a code that is compatible with the types of data sent along nerve networks.
- meanings. Another great mystery. How are meanings stored ? For a cat
or a table, presumably as some kind of pictorial representation (picture) -
associated perhaps with other information such as furry-feeling, meowing,
rectangular, etc. Perhaps the meaning of the word 'hot' is stored as memories
of hot experiences. Perhaps the meaning of the word 'two' is stored as
memories of examples of two objects.
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