Fluent speakers do not appear to have conscious knowledge of the linguistic categories and declarative rules that linguists use to describe grammar and that most psycholinguists have adopted for explaining language functioning. The implication derived in this paper is that these categories and rules are deprived of psychological reality. It is proposed that a psychologically real morphosyntax is concerned with sentence surface. The pragmatic framework and the semantic relational matrix at the onset of sentence production are converted directly into syntagmatic patterns, flexibly distributed along the sentence line. These patterns are reflected in probabilistic associations between words and sequences of words. Natural morphosyntax is learned incidentally through implicit procedural learning. Children extract frequent syntagmatic patterns from adapted adult input. The resulting knowledge is stored in procedural memory. The cortico-striatal -cerebellar system of the brain has the computational power necessary to deal with sentence sequential patterning and associative regularities.