These are competition, structural levels, and time/process frames. The classic version of the Competition Model describes and quantifies the role of competition in language. However, in a fuller emergentist account, this analysis of competition must be supplemented through an analysis of structural levels and time/process scales. Structural linguistic analysis (Harris, 1951) distinguishes the levels of input phonology, output phonology, lexicon, semantics, morphology, syntax, mental models, and interaction. Processing on these levels can be analyzed in terms of the related theories of statistical learning (input phonology), gating and fluency (output phonology), embodied cognition and hub-and-spoke theory (semantics), DevLex (lexicon), item-based patterns  (syntax), perspective theory  (mental models), and CA theory  (interaction). The theories for lexicon, syntax, and mental models have been elaborated in specific ways that help unify the approach. These elaborations include specifically the theory of item-based patterns and the theory of perspective shifting. The theory of item-based patterns is based on ideas about positional patterns from Braine (1962, 1976) that were modified by MacWhinney to restrict early patterns to individual lexical items. The theory holds that children learn item-based patterns to combine words by focusing on individual operators, such as "my" or "more". They learn these patterns as a part of their learning about the function of these operator words. They then generalize groups of item-based patterns to abstract feature-based patterns such as the one that places adjectives before nouns in English. In this way, the theory of item-based patterns can be viewed as an early instantiation of Construction Grammar , albeit one specifically designed to account for child language learning. Sentence processing involves the repeated filling (or merge or unification) of roles specified by the item-based and feature-based patterns. The linked dependency structure provide by the operation of item-based and feature-based patterns serves as the input to mental model construction. On this level, sentences encode agency, causation, reference, and space-time through a process of perspective taking. This process allows the human mind to construct an ongoing cognitive simulation of the meaning of an utterance coded in linguistic abstractions, through the use of perceptual realities derived from one's embodied experience. The perspective taking approach views the forms of grammar as emerging from repeated acts of perspective taking and perspective switching during online language comprehension. Grammatical devices such as pronouns, case, voice, and attachment can all be seen as ways of expressing shifts in a basically ego-centered perspective.