Effects of waiting times within simple problems: an analogy to waiting times in human-computer interaction

The impact of forced intra-task waiting periods was evaluated in a laboratory study designed in analogy to forced waiting periods in human-computer interaction. Each task consisted of two lines of grouped capital letters (so-called Sterzinger lines) that had to be processed individually, separated by the experimental waiting period. The final response to both lines was taken after removal of the second line. The experiment was conducted according to a within-subjects design with the order of the two factors "duration" (2 s vs. 8 s) and "variability of the waiting periods" (constant vs. variable) controlled. The dependent variables were performance indices, heart rate, electrodermal activity, and subjective measures of mood and physical complaints. The results showed effects of the duration of waiting periods for the performance and the physiological variables, and effects of the variability factor for the subjective variables. Shorter waiting periods were associated with higher scores of heart rate and skin resistance responses, variable waiting periods seemed to confuse the subjects more than constant ones. The results are discussed with respect to the effects of the two experimental factors. With respect to dialog structures in human-computer interaction, the results lead to the conclusion that response interference could be avoided by giving the user the possibility to immediately input problem solutions. Partial and preliminary inputs should be permanently kept visible during the whole task cycle by the software.