The proposed studies will examine the learning capacities of brain-damaged children through the use of two psychological paradigms which involve the use of only innocuous and non-invasive stimuli. Stimulus-stimulus association will be tested in an adaptation of the conditioned "expectancy" or perceptual disparity paradigm, and operant conditioning will be evaluated through a sensory reinforcement procedure. Results of these studies, and those on normal control infants, will provide information on a) the ontogeny of learning in the human, b) the contributions of different levels of neuraxis to learning processes, and c) the residual learning capabilities of severely brain-damaged infants. These studies will be paralleled by comparable studies in normal infant and adult rats and in surgically decerebrated rats. In addition to providing a cross species comparison and confirmation of the results in humans, these animal studies will allow a) greater experimental control and more complete documentation of the extent of brain damage and b) a more systematic examination of learning capacities than is feasible in the human. Particular attention will be devoted to the relationship of the human learning paradigms to more traditional classical and operant conditioning procedures. In the aggregate, the results of these studies will provide important information on a) theoretical issues relating to the role of different levels of the nervous system in learning processes, b) evaluation of learning capacities in severely brain-damaged infants with a limited response repertoire, and c) the development of treatment strategies to maximize the cognitive development of brain-injured children.