Impact of response delay and training on user performance with text-based and graphical user interfaces for engineering design

With recent computer advances, visualization techniques are becoming more prevalently used as decision support tools for parametric design and engineering optimization. Despite the apparent advantages of visualization techniques, we have found little evidence in the engineering design literature that assesses the impact of fast graphical design interfaces on the efficiency and effectiveness of engineering design decisions. In this paper, we present experimental results from an I-beam design problem where the importance of rapid feedback is investigated by incorporating time delays in the software response to "mimic" computationally expensive design analyses. Design efficiency is measured by recording the completion time for solving the design problem, and design effectiveness is measured by calculating the error between a submitted design and the known optimum. The impact of graphical feedback is examined by comparing user performance on three different design interfaces to determine if their functionality and graphical capabilities mediate the impact of response delays in the software or the amount of training needed. Experimental results indicate that, on average, error increased by 280% and completion time increased by 33% when a delay of 1.5 s was present, and the perceived workload significantly increased as well. Meanwhile, user performance improved and perceived workload decreased as the "richness" of the design interface increased. The combination of a rich interface with a fast response time, therefore, will lead to the "best" interface as one might surmise, but our work provides the first empirical evidence of the effect of response delay on user performance within a realistic engineering design setting. Implications for interface development for engineering design are explored within the context of our findings, as are suggestions for future work.