The relationship between post‐task and continuous‐vicarious ratings of difficulty
Richard E. Cordes · International Journal of Human-Computer Interaction · 1993
A study was conducted that used continuous‐vicarious ratings (CVRs) of difficulty to investigate how people make judgments of task difficulty. Twelve people performed five editing tasks using a text editor. After each task, the participants rated the overall difficulty they experienced in performing the task. They then viewed a videotape of their performance. While the participants were viewing the tape, they were asked to rate continuously the difficulty they felt they had experienced at that moment when performing the task. From this curve of difficulty over time, seven variables were obtained as possible candidates in predicting their overall task‐difficulty ratings. It was found that the contrast between the maximum or peak of the continuous rating and the mean difficulty level best accounted for the post‐task ratings of difficulty, followed by the time it took to perform a task. In other words, the more the peak difficulty stood out from the background average‐difficulty level combined with the more time spent performing a task, the higher the participants rated their overall task difficulty. A three‐variable (maximum difficulty, mean difficulty, and time) power‐function model was developed that best predicted the post‐task difficulty ratings. The terms in this model were statistically significant and accounted for 63% of the variability in the task‐difficulty ratings. These results imply that human factors practitioners may be more effective focusing on and improving what people judge to be the most difficult aspects of an interface. Indeed, the results suggest that concentrating on other areas to improve an interface may actually cause an increase in perceived difficulty simply because the problem causing the peak difficulty has become more salient.