claig said: "I think it is due to memory, they see how others do it and they internalise the whole words, whole sentences, whole thoughts and whole images portrayed by these words and they can then create new patterns, sentences and thoughts based on what they have seen before. They immerse themselves in words and thoughts until they become second nature, so that their ideas then flow rather than having to be developed brick by brick, sound by sound, from the bottom up."
You are entitled to think it's 'due to memory' claig and to invent a theory as to how reading and writing works if you wish.
What the research shows, however, is that there are different types of memory, based in different locations in the brain. That babies learn language by their brains forming neural pathways in response to specific speech sounds and patterns of sound. That some children figure out for themselves, consciously or sub-consciously, how our alphabetic writing system maps on to the way speech sounds make up words and sentences. And that others don't figure it out for themselves and need specific support.
In a mass education system we have to find a method or methods of teaching reading that work for all children, so it makes a lot of sense to use one that benefits as many children as possible. The evidence suggests that synthetic phonics does just that. If children can't decode they can't see how others do it. That's the problem.