In order to provide a reliable measure of the similarity of uppercase English letters, a confusion matrix based on 1,200 presentations of each letter was established. To facilitate an analysis of the perceived structural characteristics, the confusion matrix was decomposed according to Luce's choice model into a symmetrical similarity matrix and a response bias vector. The underlying structure of the similarity matrix was assessed with both a hierarchical clustering and a multidimensional scaling procedure. This data is offered to investigators of visual information processing as a valuable tool for controlling not only the overall similarity of the letters in a study, but also their similarity on individual feature dimensions.

SUMMARYRecent developments in semantic theory, such as the work of Labov (1973) and Lakoff (1973), have brought into question the assumption that meanings are precise. It has been proposed that the meanings of all terms are to a lesser or greater degree vague, such that, the boundary of the application of a term is never a point but a region where the term gradually moves from being applicable to nonapplicable.Developments in fuzzy set theory have made it possible to offer a formal treatment of vagueness of natural language concepts. In this article, the proposition that natural language concepts are represented as fuzzy sets of meaning components and that language operators-adverbs, negative markers, and adjectivescan be considered as operators on fuzzy sets was assessed empirically. In a series of experiments, we explored the application of fuzzy set theory to the meaning of phrases such as very small, sort of large, and so on.In Experiment 1, subjects judged the applicability of the set of phrases to a set of squares of varying size. The results indicated that the group interpretation of the phrases can be characterized within the framework of fuzzy set theory. Similar results were obtained in Experiment 2, where each subject's responses were analyzed individually. Although the responses of the subjects, in general, could be interpreted in terms of fuzzy logical operations, one subject responded in a more idiomatic style.Experiments 3 and 4 were attempts to influence the logical-idiomatic distinction in interpretation by (a) varying the presentation mode of the phrases and by (b) giving subjects only a single phrase to judge.Overall, the results were consistent with the hypothesis that natural language concepts and operators can be described more completely and more precisely using the framework of fuzzy set theory.Picture a conversation between a mother mother's statement. If the son had been and her S-year-old son. The son asks the asked directly how many constitute a few, mother if he might have some jelly beans he probably would have hesitated for a from the bowl on the table. The mother moment and then responded "three" (or replies that he may take a few, and he does "four," or "five," and so on). Pose the just that. It is a perfectly normal conversa-same question to the mother, and the odds tion until one stops and considers how are that she would have responded with many a few are. The mother obviously not too different a number. The number of knows what is meant by the term a few. beans taken might have differed from what The information was understood by her either person might have replied, but the son because he responded correctly to the actual number was probably an acceptable 254

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Letter series completion problems varying along location of irrelevant relations (beginning, end, none) were presented to 24 Ss. A repeated-measures analysis of solution times and errors revealed that irrelevant relations at the beginning of series produced the longest latencies and the most errors. Using a pattern induction/sequence production model of serial processing, an error analysis showed production error rate remained constant across treatments, while pattern induction errors varied with confusion location. The results indicate that the difficulty of sequential processing varies with irrelevant relations only during the pattern induction phase. The findings also support a left-right generate-and-test model of pattern induction for the task.Many theories have been advanced concerning the processing of sequential patterns (e.g