This proposal presents a set of principles of human information processing that have been developed by the investigator and describes a program of collaborative research designed to assess the adequacy of these principles for modeling cognitive processes in normal and disordered individuals. In brief, the principles state the human cognition occurs through a graded, stochastic, adaptive, interactive and distributed process. The ultimate goal is the further development and understanding of the set of principles and a further exploration of the implications of the principles for normal and disordered cognition. The principles serve as the focus of specific research projects on the following topics: general laws and regularities of information processing; the role of context in visual information processing; the mechanisms of attention and neuromodulatory deficits of attention; and the mechanisms of attention and neuromodulatory deficits of attention; and the mechanisms of accessing representations of the sounds and meanings of printed words. Each project involves the comparison of the results of computer simulation models based on the principles to the results of psychological experiments designed to produce evidence relevant to the assessment of the adequacy of the principles. The proposal also describes plans for the further incorporation of principles emerging from neuroscience and for the dissemination of concepts and simulation tools that are crucial to facilitate exploration of the principles by other researchers.