A methodology for chair evaluation.

A methodology for evaluating a single chair, rather than making a comparison among chairs, was developed from previous chair studies. The methodology was found to be rapid and effective when applied to a prototype chair, giving information to the manufacturer on overall comfort and good and bad points in the design. Testing took place on three tasks and showed that chair comfort is influenced by the task as well as the chair.

Incorporating the effect of display formats in cognitive modelling.

Cognitive modelling provides a method for identifying strategies used by people to acquire and process information. Previous research has shown that the way in which problem information is represented can have a profound effect on performance. The purpose of this study is to integrate the effects of display formats into cognitive modelling by determining the locus of that effect in information processing strategies. The research accomplished that goal by constructing cognitive models of information processing strategies using verbal protocols, and then relating those models to performance. In the process of constructing models, the study establishes a link between previous research in display formats and cognitive modelling techniques by determining how the models must be adjusted to account for the differences in performance related to a specific type of display format. The ability of cognitive modelling techniques to predict performance is discussed, and issues for further research to improve the utility of such models are presented.

Time stress and the processing of visual displays.

Selecting the appropriate display format for time-constrained tasks is the focus of the research presented in this paper. The effect of time stress on operator performance was assessed by manipulating the time available to process the display. Twenty people were trained as operators and instructed to identify the state of a system using either a digital display or a polygon display. Participants were required to reach a prespecified criterion in training and were then tested under time-constrained conditions. Time constraints were set at 100%, 50%, and 25% of each person's mean unpaced response times obtained during training. Results showed that response to the time constrained conditions was significantly affected by uncertainty and the type of display format. Discussion focuses on the effects of time stress on performance and the selection of displays for time-constrained tasks.

Effect of uncertainty and diagnosticity on classification of multidimensional data with integral and separable displays of system status.

Integrative, objectlike displays have been advocated for presenting multidimensional system data. In this research two experiments assess the effect of uncertainty on the processing of integral and separable displays. In each experiment 30 subjects were trained to classify instances of system state into one of four state categories using a configural display, a bar graph display, or a digital display. In Experiment 1 the range of instances from the state categories was uniform; in Experiment 2 the distribution was biased toward those instances of highly uncertain state category membership. After training, subjects received extended practice classifying system data. In both experiments uncertainty was found to have the greatest effect on classification performance. In Experiment 1 the bar graph display was consistently superior; the configural display was superior to the digital display only under conditions of low uncertainty. In Experiment 2 the superiority of the bar graph display diminished, producing results equivalent to those of the digital display, with the configural display producing the worst performance. The effect of uncertainty on classification performance is discussed, with specific attention paid to the apparent configural and separable properties of the bar graph display.

Minimizing the time to search visual displays: the role of highlighting.

Office computer users frequently need to search long lists of options for a particular target. Highlighting a subset of the options can shorten the average display search time. The goal of the current research was to identify the subset of options to highlight that minimizes users' average search time for any given display. To begin, a mathematical model of the visual search process was constructed which could be used to predict the average search time for a target in a display with or without highlighted options. The predictions of this model were then compared with the results of a visual search experiment that varied the type of highlighting (blocked, random, or no highlighting), the number of highlighted options, and the probability that a target was highlighted. Overall the predictions of the model were consistent with the results from the experiment. Finally, procedures based on the model were developed which could be used to find the optimal subset of options to highlight for a given display--that is, the subset of highlighted options that minimizes users' search times.