Examining the Effect of Interruptions at Different Breakpoints and Frequencies Within a Task

Research on the effects of interruptions shows that they can be either costly or beneficial depending on which aspects of an interruption are manipulated. One important aspect that contributes to these conflicting results concerns when an interruption occurs. The present study explored how event segmentation theory (EST) can be used to determine optimal moments for an interruption relying on hierarchical task analysis (HTA) to identify coarse and fine event boundaries. Utilizing a 2 X 3 mixed design, undergraduate students completed a trip planning task divided into three task trials. The within-subjects factor was interruption timing, which had three levels: none, coarse breakpoints, and fine breakpoints. The between-subjects factor was interruption frequency, which had two levels: one and three. According to memory for goals theory (MFG), a task representation at a fine breakpoint is large and thus an interruption occurring at this breakpoint increases memory demand and results in performance decrements when compared to an interruption at a coarse breakpoint. In line with this theory, it was hypothesized that interruptions would be more disruptive at fine vs. coarse breakpoints and that as the frequency of interruptions increased, so would the degree of disruption. Last, it was expected that the effects of high frequency interruptions would be more pronounced at fine vs. coarse breakpoints. The dependent measures included resumption lag, task completion time, number of errors, mental workload, and frustration. The findings provided partial support for these predictions. Consistent with MFG theory and EST, participants took longer to resume the primary task and reported higher mental workload and frustration when interruptions occurred at fine breakpoints. Conversely, the effects of interruptions at coarse breakpoints were similar to completing the task without interruption. However, interruption frequency had no effect on performance. In general, these results suggest that the disruptiveness of a single or even a few interruptions is tied to the point within the task hierarchy where it occurs