Thomas K. Landauer

Structural differences between common and rare words: Failure of equivalence assumptions for theories of word recognition

Theoretical discussions of word frequency effects often assume words of different usage frequencies to be equivalent in other respects relevant to perception. Such assumptions were found to be unwarranted. In Study I, common as compared to rare words were found to be confusable with a greater number of other words by a substitution of a single letter. Moreover, the average usage frequency of such “neighbors” was higher for common words. In Study II, common and rare words were found to contain different distributions of phonemes and graphemes. In Study III, one-syllable words containing phonemes typical of common as compared to rare words were found to be more intelligible, ceteris paribus . The relation of these findings to theories of word-frequency effects is discussed.

Memory Without Organization: Properties of a Model with Random Storage and Undirected Retrieval

A very simple spatial model of memory storage and retrieval is described, analyzed, and discussed. The postulated memory is without organization in the sense that neither the place of storage nor the order of search during retrieval is influenced by the nature of the information being stored or retrieved. The memory consists of a three-dimensional space containing a large number of homogeneously distributed loci at which data may be stored. Data received near each other in time are stored at nearby locations. Access is by an undirected expanding-sphere search. The model exhibits a wide variety of quantitatively and qualitatively humanlike behavior with respect to both standard learning and forgetting paradigms and with respect to frequency effects and other phenomena in word processing.

Natural command names and initial learning: a study of text-editing terms

In the first of two studies of “naturalness” in command names, computer-naive typists composed instructions to “someone else” for correcting a sample text. There was great variety in their task-descriptive lexicon and a lack of correspondence between both their vocabulary and their underlying conceptions of the editing operations and those of some computerized text editors. In the second study, computer-naive typists spent two hours learning minimal text-editing systems that varied in several ways. Lexical naturalness (frequency of use in Study 1) made little difference in their performance. By contrast, having different, rather than the same names for operations requiring different syntax greatly reduced difficulty. It is concluded that the design of user-compatible commands involves deeper issues than are captured by the slogan “naturalness.” However, there are limitations to our observations. Only initial learning of a small set of commands was at issue and generalizations to other situations will require further testing.

Category Size and Semantic Memory Retrieval.

When a person judges whether a test word like COLLIE belongs to a specified semantic category like DOGS, reaction time varies directly with category size. This finding has implications for theories of human semantic memory. Collins and Quillian (1970) claimed that the apparent effect of category size is due to variations in the degree of semantic relatedness between test word and category. The present paper reports data demonstrating a category-size effect that is independent of semantic relatedness. A simple category-search model is considered that explains the category-size effect more directly than does the Collins and Quillian model. Some relevant methodological and theoretical problems are also discussed.

Determinants of reaction time for digit inequality judgments

Moyer & Landauer (1967) found that reaction time to indicate the larger of two digits was well described by an equation proposed by Welford (1960) as a general description of decision times for inequality judgments about perceived physical magnitudes. Moyer and Landauer suggested, therefore, that perceptual and symbolic inequality judgments might be based on similar processes. Parkman (1971) presented seemingly contrary evidence, but reanalyses of his data show that they are, in fact, fully consistent with our original account.

Memory for at least one of two items: Test and failure of several theories of spacing effects

Spacing between two attempts to learn one item greatly increases the probability that it will be remembered later. We first note that a number of theories that explain this phenomenon also predict that spacing should improve the probability of remembering at least one of two different items each studied once. We then report results of two experiments designed to test this prediction. Subjects studied a series of 300 words. After a short rest they were tested for recognition, or—in the second experiment—free recall and then recognition. As usual a substantial spacing effect was observed for single words presented twice. In contrast the probability of correct recognition or recall of at least one word of a pair of two different words, each presented once, did not depend on their spacing in the study series.

Using examples to describe categories

The successful use of menu-based information retrieval systems depends critically on users understanding the category names and partitions used by system designers. Some of the problems in this endeavor are psychological and have to do with naming large and ill-defined categories so that users can understand their contents, and effectively partitioning large sets of objects. Systems of interest (like home information systems) often consist of new and frequently changing content in large and varied domains, and are particularly prone to these problems. We explored several ways in which one might name categories in one such domain (Yellow Page category headings) - category names, category names plus examples, and examples alone. We found that three examples alone were essentially as good a way to name these categories as either an expertly chosen name or a name plus examples. Examples provide a promising possibility both as a means of flexibly naming menu categories and as a methodological tool to study certain categorization problems.

Exams and Use as Preservatives of Course-Acquired Knowledge.

AbstractRetention of material learned in college-style technical courses was measured by a repeated final examination given one year later. Matched groups of students also repeated the final examination six weeks or six months after the end of the courses. The six-month group showed almost no loss over the year. The six-week group suffered about the same considerable loss as did a control group with no intervening examination. Questionnaire measures indicated that students who used over 10 percent of the examined material in their average monthly work also forgot very little. Apparently, course-acquired knowledge can be kept fresh over long periods by small amounts of properly spaced review activities.

Can simple instructions to use spaced practice improve ability to remember a fact?: An experimental test using telephone numbers

As part of class demonstrations, college students were given single seven-digit telephone numbers and asked to memorize them according to one of two different sets of instructions. Control instructions asked the students to memorize the number as they “normally would.” Experimental instructions recommended a form of spaced practice. After 2 weeks, recall was tested and confidence ratings obtained. The spaced-practice instructions produced significantly better recall than did control instructions. Confidence in incorrect answers was slightly lower in the experimental than in the control group, indicating that recommending the study method did not engender false confidence. Thus, merely prescribing spaced practice can help people memorize more effectively.

Consolidation in human memory: Retrograde amnestic effects of confusable items in paired-associate learning

Keeping the total set of presented pairs constant, the position of occurrence of potentially interfering pairs relative to “critical” pairs was varied. A critical pair is remembered less well if interfering material follows it closely than if the interfering material is postponed. As the interval between a critical pair and interfering material is increased, long-term retention of the critical item improves. Comparable variations in the position of interfering material before a critical item do not affect its retention. These results suggest the existence of a post-exposure consolidation process, and are inconsistent with certain kinds of discrimination and coding theories of paired-associate learning.