I can't say whether spoken language is more important than written language and vice versa. The most common observation during childhood is that children merely focuses on what they hear and not on what they see. People think that oral language is the first thing a child develops as it learns to communicate with its environment. However, this has been disproved by recent scientific studies. The truth is that children first develops communication skills through the written language. Our brain is so powerful that it directly interprets anything it visualizes. It creates patterns that helps the learning process much faster and the ability to communicate much easier.
Before a child could speak, he will first evaluate his environment. As a child grows older and starts to explore the world, signs, symbols, colours, sounds etc., becomes their constant company. A child's brain will collect and interpret everything it encounters (may it be symbols or sounds) to which a child will truly understand as it comes of age.
Oral language and written language is part of our daily lives. They're part of our civilization. They're part of the building blocks of a society, communication that is. Both a necessity. An essential role to everything we do. Oral language and written language is interrelated that one cannot exist without the other.
