Simplify the following text for a Grade 14 native English-speaking person.
Original: Argyle ( 1970 ) put forward the hypothesis that whereas spoken language is normally used for communicating information about events external to the speakers , non-verbal codes are used to establish and maintain interpersonal relationships .
Simplified: Argyle ( 1970 ) put forward the idea that spoken language is mainly used for communicating information about external events , and non-verbal codes are used in interpersonal relationships .