The central theme of this work is the interaction and the influence of grammatical input as an external factor in language acquisition and in learning strategies and learning processes as cognitive requirements. Until now, this problem has been viewed from the perspective of explicit and implicit processes, including concepts such as consciousness/unconsciousness, outer rules/inner rules, and analysed/unanalysed knowledge. But because of these differing interpretations, how the learner uses grammatical input and what role that plays in the development of the target language has only been minimally investigated. In the tradition of interlanguage theory, and based on connectionist, information processing and variability theories, in this work a descriptive model is developed that describes acquisition at the level of processing and that helps to explain developmental patterns which are observed in the acquisition of German verb morphology by tutored learners. The specific cognitive processes involved in L2 acquisition are differentiated as three dimensions that are conceptualized as continua: 1. The dimension of selective attention and intake which is defined by the two poles of attention to form/attention to meaning and understanding/noticing. This dimension is dependent on the situational context (formal/informal style) and determines whether verb forms are learned as analysed or unanalysed regarding their function in the target language. 2. The dimension of storage of information in which form-function mappings in short-term memory become permanent routines by associative connection. 3. The dimension of development in which analysed form-function mappings arise out of unanalysed routines by restructuring. The confirmation of these processes rests on an analysis of written data from Swedish learners at the beginning and advanced levels. They were elicited over two years and were based on the use of different written tasks. The results of this investigation indicate that German verb morphology is not acquired from rules but rather by associative connections of different kinds of form-function mappings in a network. This process can be described in acquisition phases, developmental sequences, and an acquisition order.