Gary Dell's work deals with how people produce and understand sentences, and how these processes can be modelled using neural networks. For example, his research on language production attempts to understand production errors or "slips of the tongue." He has developed a neural net model that makes predictions about the qualitative and quantitative properties of speech errors. These predictions are tested using experimental procedures in which subjects produce words and sentences under controlled conditions. A particularly interesting aspect of the model is that it can be used to understand patterns of behavior resulting from brain damage. By changing the processing characteristics of the model, one can produce speech error patterns that are characteristic of certain types of aphasic patients.