Investigating the Effects of Trends in an Interface to a Dynamic System

Abstract: Uppsala University and Trafikverket (The Swedish Transport Administration) have been in collaboration in order to improve the train traffic control systems in Sweden for many years. As a result, a train traffic control system STEG (Swedish for 'Control via an Electronic Graph') was built, and evaluated. Based on the evaluation results, need for more constrained experiments have been revealed. The use of microworlds in such dynamic decision making research is a common approach. For that reason, a microworld (train traffic simulator) was built in Uppsala University. The purpose of the designed experiment was to explore the effects of absence or presence of trend lines on performance and perceived difficulty in an interface of a dynamic system for novice users. The study also answered whether instead of a generic goal, introduction of a target to the users affected their behavior. In the experiment, 32 participants, interacting with the microworld, tried to solve a logical problem and were given 40 trials to improve their performances. In order to test main and interaction effects between the proposed variables (performance, perceived difficulty), the experiment was based on a 2 x 2 factorial design (trend lines: present/absent, target: present/absent). The results were analyzed by means of a mixed design ANOVA for repeated measures. In addition, Scheffé post-hoc analysis and regression analysis were conducted. The analysis results have shown that the trend lines did not improve performance and slowed down learning. The users who were subjected to trend lines and were introduced to a target perceived the task significantly harder.