Guy Karnas

Level of experience in text-editing: the role of mental representations on performance

Abstract 15 subjects experienced with text-editors and 15 computer naives had to learn a new text-editor and to correct a text with it. From the results and the analysis of their errors, differences between a text on screen and the representation the naives have of a text on paper are inferred. It is also shown that experienced users may perform at the level of naives if the system they use presents some novelty as compared to the majority of the applications of the same type they know.

On task context and set solutions to water jar problems

A test of 6 training and 20 main problems elaborated on a model similar to the model which underlies water-jar problems is described. The training problems and instructions require that each problem may have more than one solution. The 20 main problems can be solved by the same formula (set solution), but 10 of these problems (the test problems) can also be solved by a shorter formula (non-set solution). The score is the number of non-set solutions for the 10 test problems. A comparison between an individual condition of testing for 21 subjects and a collective condition (40 subjects tested in a group) shows a significant difference in frequency distributions of scores. More subjects gave a small number of non-set solutions in the group condition than in the individual condition. For the two conditions, data show significantly more non-set solutions to the last test problems than to the first test problems.