Technological advances are increasing the availability of displays capable of portraying large amounts of computer generated graphic information. These displays are advantageous when substantial amounts of information have to be integrated as part of a decision making process. Examples of these high density displays include tactical situation maps used by the military and certain CAD/CAM applications. Unfortunately, a problem can arise when using these displays. This occurs when the quantity of information presented becomes great enough to cause a deterioration in the user's ability to effectively process it. The resulting situation is one in which decisions are based on an incomplete use of available data. The present study addresses this problem by evaluating an aid (selective deletion) designed to allow users to deal effectively with greater amounts of information. It is based on the assumption that, while the collective uses of a display may require a large amount of portrayed information, individual tasks often do not. Selective deletion allows users to temporarily remove information that is not necessary for solving the task under consideration. It was hypothesized that the lower display density would improve the speed and accuracy of problem solving. The displays used in the present study were computer generated tactical military maps containing various terrain features and symbols for three different types of military units (Infantry, Artillery and Armor). The display was generated on a high resolution (1024×1024) color CRT. Two variables were manipulated during the experiment: information density and task type. To vary information density the number of unit symbols on a map was varied. Two density levels were used for each of three tasks. The tasks were chosen as representative of simple components of the more complicated tasks performed by the tactical analyst. Each task was run as an independent experiment. The first was a counting task requiring subjects to determine the number of units of a specific type. The second, slightly more complicated task, required subjects to solve problems in which they had to take into account the spatial relationship between unit symbols. In the third task subjects had to recognize and use certain relationships between units and terrain features in solving problems. None of the tasks required the subject to use all three unit types. Thus, the density of information on the screen could be reduced by deleting the symbols for extraneous unit types. In the experimental condition subjects would delete these extraneous units before solving the problems. In the control condition they would work with screens at full density. Subjects served as their own controls, solving problems under both conditions with the order varied across subjects. Both accuracy and speed were measured. Results show: a) The selective deletion technique greatly increases the accuracy and speed with which subjects can deal with high density visual displays. b) The density level at which the technique begins to improve performance varies with type of task. c) All subjects were aided by the technique, but there were individual differences in the density level at which it became most useful. This study has shown the selective deletion technique to be highly useful in improving a subject's ability to process information presented in high density tactical map displays. It is felt that these results will also be useful in the design of other types of computer generated visual displays. Specific examples, provided in the presentation and a follow up paper, indicate the magnitude of the effect as a function of display density and type of task, and should help guide the use of selective deletion in the design of a wide range of displays.
Slow waves, synaptic plasticity and information processing: insights from transcranial magnetic stimulation and high-density EEG experiments
