An experiment demonstrating the effect of busyness of library staff on the frequency of approach by users is presented as an example of applying a scientific approach to the problems of the librarian-client interface using the methodology of the experimental psychologist. This methodology is explained and a review of the literature on librarianship and psychology, including three surveys indicating user reluctance to approach library staff, is provided. The experiment was conducted in Edinburgh University Library over a 2-week period in November 1978 at an information desk staffed by female assistants. The results indicate that a librarian who does not appear busy will be approached between 70 percent and 80 percent more frequently than a librarian who appears busy, even though the inquirer's perception of the librarian's approachability is comparatively neutral; however, the sex of the inquirer and the nature of inquiries, in terms of their relative complexity, are seen to be independent of the librarian's busyness. Recommendations are made concerning the further use of psychological research in the field of librarianship and information science, particularly as a means of establishing a scientifically valid literature of librarian-client behavior. Twelve tables, a 51-item bibliography, and an appendix listing inquiries recorded during the experimental period are provided. (Author/ESR)