Focusing on human cognition, which some psychologists view as an interdisciplinary area of study, this volume in the "Nebraska Symposium on Motivation" present six original and provocative papers--three of them emphasizing "structural" aspects of cognition such as knowledge structures and units, conceptual and categorization processes, and semantic memory models, and three relating primarily to the attentional, perceptual and performance aspects of cognition.In the opening paper, "The Development of Attentional Mechanisms," Michael I. Posner and Mary Kay Rothbart argue that despite recent criticisms of laboratory methods employed by cognitive psychologists, techniques which are designed to trace information flow offer a basis for bridging psychological and physiological analyses, particularly in the area of attention. David LaBerge's paper, "Unitization and Automaticity in Perception," is concerned with the development of a high level of perceptual processing efficiency in tasks, such as reading, for which extremely intense and sustained training is undertaken."Motivated Retrieval from Archival Memory," by Raymond Nickerson, shows that with the application of a variety of approaches to the study of motivated retrieval, some interesting properties of memory emerge which bear upon the brand issues of content, selectivity, and representation of information in memory as well as upon the recall process itself. In "Concepts, Propositions, and Schemata: What Are the Cognitive Units?" John R. Anderson considers the nature of the information pieces or packages that constitute mental data and the role of unitization in information manipulation within active memory. Edward E. Smith, in "Organization of Factual Knowledge," stresses that the elaboration of input material is one of the most crucial review of recent research in prose communication develops a description of knowledge representation which he calls the higher unit hypothesis. The final paper, "Can We Have a Fruitful Cognitive Psychology?" by James J. Jenkins, constitutes a criticism of both the current state of knowledge about cognitive psychology and the criteria by which research progress within the field evaluated, and offers examples of promising approaches to cognitive psychology.