| On-line catalogs are replacing card catalogs in libraries. This paper reviews research covering the catalog's human-machine interface with emphasis on the difficulties of subject searching. Study 1 replicates previous findings that subject searching, though most often used, is the most problematic type of searching. In Study 2, the organization of the Library of Congress Subject Headings is compared with the knowledge structures of subject experts, subject novices, and librarians. Experts and novices in cognitive psychology differ from each other and from the subject heading structure, but librarians fall in between the two groups. The structures derived are used in Study 3 to predict the success of searching done by subject area novices and experts as well as by librarians. Experts in cognitive psychology find target books more easily than novices, but differences between librarians, subject experts, and subject novices are due to system experience, not subject expertise. |
