Humans have been smiling, gesturing and talking to one another for millions of years, but writing as a channel of communication is only about 5,000 years old. All the earliest known writing systems operate on the principle of one symbol for each word. Their symbols are logographs in which little or nothing of the sounds of words is encoded into the symbols. Some modern writing systems have persisted with this principle, notably Chinese. English spelling is another obstacle that must be surmounted by the apprentice writer. A spelling does not have to come either from the graphemic output lexicon or from phoneme-grapheme conversion. Picture writing systems, the precursors of true writing, served a number of social functions apart from transmitting love letters. A point that emerges very clearly from the work by Hayes and Flower is that planning, translating and reviewing do not occur in a linear order as discrete stages, but are closely intertwined in the writing process.