> language evolutionary theorists believe that language evolved as humans gathered to form larger social units. Language: a system of symbols and rules for combining these symbols in ways that con produce an almost infinite number of possible messages or meanings. Three properties: language is symbolic: uses sounds, written signs, or gestures physically present can be symbolically represented. Psycholinguists: study the psychological properties of language and the underlying mechanisms that produce it. Surface structure: the way symbols are combined within a given language rules for these combinations is syntax: rules of grammar. Deep structure: the underlying meaning of the combined symbols the rules for connecting the symbols to what they represent are known as semantics. Recall deep structure easier than surface structure (meaning over specific words) Phonemes: the smallest units of sound that are recognized as separate in a language . Capable of producing hundreds, but most languages use 40-50.