A distinction has to be made here between spoken language which is generally considered to be more interpersonal than informative, and written language which is considered to be primarily transactional. These two types of language are produced differently and have distinct effects.
Spoken versus written language
There are differences between spoken and written language which refer not only to the way in which they are produced and to their effects, but also to their evolution and independence. Language is considered to be a natural ability, the capacity to acquire it being innate. Still, the views are different when referring to spoken or written language. There are many linguists who believe that written language is a human invention and not a natural ability. Darwin (1871) wrote about the instinct of speaking that we can observe even with little children while there is no such instinct as writing that can be observed with children. Saussure (1916) stated that writing exists only to represent speech, while Bloomfield (1933) claimed that writing is only a way in which speaking can be recorded, there being no such term as written language. Even if this view about writing has been sustained by many renowned linguists, it is not universally accepted. Linguists from the Prague Linguistic Circle, such as Pulgram (1965) or Vachek (1973, 1989), view written language as an independent system equal to spoken language, the two systems mutually influencing each other . Goody (1977) speaks about a strong relationship between speech and writing, but he also includes a third element, language, the connection being made between these three elements. Aaron and Malatesha Joshi (2006:263) argue that, based on its adaptive value, its evolution over time and its relative independence of spoken language, "written language is yet another manifestation of the natural endowment of the human mind and may not be treated as a proxy of speech".
Halliday (1985:79) states that "The spoken language is, in fact, no less structured and highly organised than the written. It could not be otherwise, since both are manifestations of the same system." In addition, because of the latest development in science and technology, the spoken and written forms of language are no longer separated, their complementarity being widely accepted. In conclusion, whether the spoken and the written language are independent systems Pulgram (1965) and Vachek (1973, 1989) or one and the same system (Halliday (1985), their relationship has been almost generally accepted, both being means of communication with their own characteristics and with an influence on each other. If we refer to the production and effects of the spoken and the written language, we can clearly make a distinction between the two of them.
When speaking, the sender tries to influence the listener and besides the voice effects, he/she also has the advantage of using the appropriate tone of voice and body language in order to emphasize what he/she wants to say. If using the right gestures and tone, he/she will sound more convincing. Thus, if someone says " 'I'd really like to', leaning forward, smiling" and with a warm voice, he/she will sound more convincing than a person who says the same words "leaning away, brow puckered" with a sneering voice (Brown and Yule, 1983:4). Both the speaker and the writer can control what is said/written, but the speaker has to be more careful, he/she has to know exactly what he/she has just said/is going to say so as to control the content of the message and to express exactly what he/she intends. In order to be effective, the speaker must exploit the dynamism of oral communication, but also to learn to work within its limitations. Spoken language is context bound, the speaker having the possibility to make reference to the context, the surroundings as both speaker and receiver are present in the same place, at the same time. The speaker also has the possibility of not being very explicit because if there is any misunderstanding or confusion on the part of the hearer, he/she can ask for additional information immediately, or, on the contrary, there may be no need for additional information because the two share background knowledge and there may be no need to fill in any piece of information. However, the speaker has more ability to engage the audience psychologically and to use complex forms of nonverbal communication. On the one hand, the speaker has the advantage of receiving immediate feedback form the listener(s) but also of changing the message if he/she sees that the interlocutor has a different reaction than that expected. On the other hand, the speaker is put under pressure because the listener may react to the message and expect a concise response from the speaker, thus he/she has to be able to respond quickly, but also to know how to "fix" something that he/she did not intend to say.
In writing, the focus is on the product and not on the process of production and the writer does not have an instant power over the reader because he/she does not have a direct contact with the reader, they have a minimal context bound relationship. In writing it is not enough to just put the words in the right order, but also to use the correct punctuation and grammatical structures and also to fill in as much background information as possible so as not to have a confused receiver because he/she does not have the possibility of asking for clarifications. However, the writer has control over what he/she writes. He/She is not under pressure because the interlocutor cannot intervene and interrupt him/her. The writer can also correct or change what he/she does not like, without being necessary to justify his/her actions in front of the readers. He/She has the opportunity to be organised and give dense and concrete information. Still, he/she does not have an immediate response from the interlocutor and can only imagine what his/their reactions would be. (Brown and Yule, 1983)
In conclusion there are advantages and disadvantages for both speakers and writers, and there is more power of control from the part of the writer. Still, writing is a fairly static form of transfer while speaking is a dynamic process by which information is transferred.