In two experiments novice computer users were taught a text editor from one of a set of manuals describing the commands and their functions. The manuals varied systematically in how information was presented. In Experiment II (the more extensive study) half of the 72 college subjects got the commands via an “abstract syntax”, following the presentation style of the original manual for the system. For the other half of the subjects the commands were presented in a more concrete form. Crossed with the syntax variable was one of manual organization. For half the subjects the manual presented many alternative ways of accomplishing a sub-task as soon as that sub-task was introduced—again following the original design of the manual. For the other half the alternatives were minimized at the introduction of the sub-task, but all were provided before the editing itself began. A third variable was also studied: presence vs absence of a surrogate model (a mental model) for the editor. Half of the subjects were presented with such a model and half were not. A time-stamped keystroke record was kept while the subjects tried to use the editor, and a variety of dependent variables involving accuracy and speed were measured. The results showed significant effects of the manual variables (syntax and organization), though the locus of the effects—the dependent variables influenced—varied between the two independent variables. The surrogate model had little effect. The results are discussed in terms of the planning and execution stages of novices' performance and how the independent variables affect these stages.
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