Three experiments explored memory for symbolic circuit drawings using skilled electronics technicians and novice subjects. In the first experiment a skilled technician reconstructed circuit diagrams from memory. Recall showed marked "chunking", or grouping, by functional units similar to Chess Masters' recall of chess positions. In the second experiment skilled technicians were able to recall more than were novice subjects following abrief exposure of the drawings. This advantage did not hold for randomly arranged symbols. In the third experiment the size of chunks retrieved systematically increased with additional study time. Supplementary analyses suggested that the chunking by skilled subjects was not an artifact of spatial proximity and chunk statistics, and that severe constraints are placed on any explanation of the data based on guessing. It is proposed that skilled subjects identify the conceptual category for an entire drawing, and retrieve elements using a generate-andtest process.The skill of reading nonverbal, symbolic drawings is important for a wide range of occupations including electronics, engineering, chemistry, and architecture. A skilled electronics technician, for example, must be able to understand complex configurations of symbolic circuit elements, and relate these configurations to hardware in need of repair and to the requirements of circuit design problems. While it seems clear that people become more proficient at this sort of skill as a result of training and relevant experience, it is by no means certain how the irnprovement should be characterized at the level of mental processes. The present studies were carried out to obtain a more precise description of what it is that people who are skilled at reading symbolic drawings actually know. This kind of description may be useful for later applications aimed at assessing the skill level of people, developing job aids for skilled performance, or improving training in such skills.The previous research most relevant to understanding the skill of reading symbolic drawings concerns the striking effects of experience on the recall of chess and Go positions. DeGroot (1966), for example, showed that a Chess Master could correctly replace from memory 91% of the chess pieces in amidgame position (approximately 22 of 24 pieces) after only a 5-sec study of the board. A "weak" player could replace only 41% of the pieces correctly.

No abstract

SuperBook is a hypertext browsing system designed to improve the usability of conventional documents. Successive versions of SuperBook were evaluated in a series of behavioral studies. Students searched for information in a statistics text. presented either in conventional printed form or in SuperBook form. The best version of SuperBook enabled students to answer search questions more quickly and accurately than they could with the conventional text. Students wrote higher quality "open-book" essays using SuperBook than they did with the conventional text, and their subjective ratings of the documentation strongly favored SuperBook.This work is a case study of formative design-evaluation. Behavioral evaluation of the first version of SuperBook showed how design factors and user strategies affected search and established baseline performance measures with printed text. The second version of SuperBook was implemented with the goal of improving search accuracy and speed. User strategies that had proved effective in the first study were made very easy and attractive to use. System response time for common operations was greatly improved. Behavioral evaluation of the new SuperBook demonstrated its superiority to printed text and suggested additional improvements that were incorporated into "MiteyBook," a SuperBook implementation for PC-size screens. Search with MiteyBook proved to be approximately 25 percent faster and 25 percent more accurate than that obtained with a conventional printed book.

The study concerned (a) identifying component processes of discovery and rule learning; (6) describing differences in learning outcomes produced by the two instructional methods; and (c) optimizing learning.In two experiments, subjects acquired concepts of probability by discovery or rule versions of programmed instruction. Several skills important to successful learning by discovery were found to be less essential to successful learning by rule. Results also supported the hypothesis that the outcome of discovery is the structural integration of previously known concepts, while the outcome of rule learning is the addition of new structure. Finally, subjects scoring low on tests of relevant abilities performed better by every measure when instructed by the rule method.

Why do some people have much more difficulty than others in learning a computer-based skill? T o answer this question, we observed first-time users of computers as they learned to use a computer text editor. In two experiments, older people had more trouble than younger people and those who scored low on a standard test of spatial memory had greater diffkulty than high scorers. These correlations were stable over several hours of practice and did not vary as a function of the type of terminal used or specific editing problems attempted. Correlations involving age and spatial memory could not be explained by other characteristics such as amount of education, reasoning ability, or associative memory ability. Results like these that relate learning diffkulty to specific characteristics of people ultimately may suggest ways to change computer interface design or training to accommodate a wider range of users.