Book excerpt: The topic addressed in this volume lies within the study of sentence processing, which is one of the major divisions of psycholinguistics. The goal has been to understand the structure and functioning of the mental mechanisms involved in sentence comprehension. Most of the experimental and theoretical work during the last twenty or thirty years has focused on 'first-pass parsing', the process of assigning structure to a sentence as its words are encountered, one at a time, 'from left to right' . One important guiding idea has been to delineate the processing mechanisms by studying where they fai!. For this purpose we identify types of sentences which perceivers have trouble assigning structure to. An important class of perceptually difficult senten ces are those which contain temporary ambiguities. Since the parsing mechanism cannot tell what the intended structure is, it may make an incorrect guess. Then later on in the sentence, the structure assignment process breaks down, because the later words do not fit with the incorrect structural analysis. This is called a 'garden path' situation. When it occurs, the parsing mechanism must somehow correct itself, and find a different analysis which is compatible with the incoming words. This reanalysis process is the subject of the research reported here.