MENUS AND MEMORY LOAD - NAVIGATION STRATEGIES IN INTERACTIVE SEARCH TASKS

When tasks offer alternative methods for attaining subgoals, several factors may determine which method is selected. People might choose procedures that are, or appear, cognitively less demanding. These demands can operate over several different dimensions (e.g. learnability, solution speed, number of motor actions). A series of studies is reported of method selection for a task that involved locating and comparing information within an electronic document. A variety of computer-based memory aids were also available to readers. Experiment 1 showed that subjects' navigation choices were predicted more successfully by a GOMS analysis than by the number of discrete actions (mouse clicks) required for the alternative procedures. However, the GOMS model failed to predict subjects' choices in experiment 2 where the previously chosen navigation method was modified to increase its procedural length and reduce its perceptual affordances. Subjects still frequently chose this navigation method but they also significantly increased their use of memory aids. Experiment 3 examined whether subjects' navigation choices arose from the memory demands of the alternative methods. The reults showed that the method rejected by subjects in experiment 2 gave faster performance and reduced the use of some of the memory aids. It is suggested that number of motor actions in a procedure determines the use of memory aids but not the selection of navigation method. The perceptual characteristics of the alternative methods, which may relate to factors such as subjective risk, need to be incorporated into models predicting the procedures that people will select in complex tasks.