[Added June 2005]
The voice in the head ,when we read silently, is indeed a voice! Experiments
have shown that we really hear the sound of a voice reading the text (i.e.
it is as if the brain runs an experiment simulating ourselves that read the
words in the text aloud and then understands the meaning of the written text).
The visual pattern of words plays no role in understanding. The Chinese
people also, when read silently , understand the written text because of the
sound heard and not because of the pattern of ideograms.
For the same reason deaf people have problems learning to read.
From the same fact comes a suggestion to improve learning of new languages:
when you read a text , always imagine hearing the sound of the words also if
you don’t know exactly the correct sound.