Mental effort with the use of different dialogue techniques in human-computer interaction

Flexibility is an important design criterion for user interfaces of interactive computer systems. Flexibility should allow an adaptation of the system to inter- and intra-individual differences in users. Flexible design requires to know how users base their decisions when they select one of the various options for interaction offered by the system. This problem has been studied in a psychophysiological experiment. In the experiment subjects were required to create graphics on a screen. Independent variables were: experience of the subjects (varied by training sessions), dialogue technique (menues vs. command language) and tasks. Tasks were constructed and analyzed by Cognitive Complexity Theory in order to have tasks suited for either menue or command techniques. Mental effort was registered by P300-amplitude of evoked potentials in the preparation stage of interaction and by 0.10 Hz-component of heart rate variability during the execution stage. It was possible to identify decision strategies based on anticipations of cognitive effort by considering the technique preferences shown in the training sessions and the time subjects spent on the task analysis.