Mental representation - cognitive representations of the world, including images, ideas, concepts, and principles, that are the foundations of thinking and problem solving. Rules for these combinations are syntax (rules of grammar) Semantics - rules for connecting the symbols to what they represent. Displacement - refers to fact that past, present, future, and imaginary events and objects that are not physically present can be symbolically represented and communicated through the medium of language. Language is symbolic, has structure, and is generative. Surface structure - consists of the way symbols are combined within a given language. Deep structure - refers to the underlying meaning of the combined symbols. Phonemes - smallest units of sound that are recognized as separate in a given language. Morphemes - smallest units of meaning in a language (syllables) Language-deprived children found at 6 years old seemed to be able to develop normal language abilities.