Final answer:
George Herbert Mead proposed the idea that speech develops into speech directed at other people and speech directed at themselves.
Step-by-step explanation:
The idea that speech develops into two types--speech directed at other people and speech directed at themselves--was proposed by George Herbert Mead. Mead, a philosopher and sociologist, focused his work on how the mind and the self are developed as a result of social processes. He emphasized that an individual's self is developed through social interaction and that we are not born with the ability to view ourselves from the perspective of others. This ability, according to Mead, is learned through socialization, which allows us to become self-aware by looking at ourselves from the viewpoint of 'the other'.