A great deal of everyday human activity is spent acquiring visual information from the environment and using this information to guide behavior. The proposed research is designed to investigate the perceptual and cognitive processes by which visual information is acquired and which result in a long-term memory representation of the acquired information. The research concerns perception of, and memory for, relatively complex visual material (mostly natural scenes). Three lines of empirical investigation are proposed. The first of perceptual processing, that is processing that operates on the visual information present in e environment. The second is of conceptual processing, that is processing that is carried out in short-term memory, and eventuates in the picture's long-term memory representation. The third is of priming, that is, the means by which semantic information, provided just before a picture's appearance, influences visual processing of the picture. In many (although not all) of the experiments, the general paradigm is the following. Pictures are presented for varying durations (e.g., from 30 to 500 milliseconds) and memory performance for the pictures is subsequently measured. Memory performance to exposure duration (called a performance curve) represents the temporal course of processing. Comparisons of performance curves obtained under different levels of some variable (e.g., for dim vs bright pictures) permits an assessment of the variable's effect on picture processing. Associated theoretical investigation is proposed. All experiments are intended to guide and test existing theories of perceptual and conceptual processing that have been proposed by the PI and by others. These theories are all formally and quantitatively specified; hence their predictions with respect to the proposed experiments are clear and unambiguous. Data and theory about normal visual processing provide a foundation for isolating causes of, and guiding solutions to abnormal or suboptimal visual processing. Suppose, for example, that an individual complains that he or she "just can't seem to keep up with what's happening in a complex visual environment." What is causing this problem? Is it, for example, simply a slowing of initial information acquisition? Is it a lack of ability to use appropriate contextual information to guide processing? Is it a lack of ability to manipulate acquired visual information in short- term memory? The proposed research will provide the empirical and theoretical technology that would enable a clinician to differentiate among these (and other) possible reasons for the difficulty.