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

What makes an interruption disruptive? Understanding the effects of interruption relevance and timing on performance

Interruptions disrupt activity, hindering performance and provoking errors. They present an obvious challenge in safety-critical environments where momentary slips can have fatal consequences. Interruptions are also a problem in more workaday settings, like offices, where they can reduce productivity and increase stress levels. To be able to systematically manage the negative effects of interruptions, we first need to understand the factors that influence their disruptiveness. This thesis explores how the disruptiveness of interruptions is influenced by their relevance and timing. Seven experimental studies investigate these properties in the context of a routine data-entry task. The first three experiments explore how relevance and timing interact. They demonstrate that the relevance of interruptions depends on the contents of working memory at the moment of interruption. Next, a pair of experiments distinguish the oft-conflated concepts of interruption relevance and relatedness. They show that interruptions with similar content to the task at hand can negatively affect performance if they do not contribute toward the rehearsal of goals in working memory. By causing active interference, seemingly useful interruptions that are related to the task at hand have the potential to be more disruptive than entirely unrelated, irrelevant interruptions. The final two experiments in this thesis test the reliability of the effects observed in the first five experiments through alternative experimental paradigms. They show that relevance and timing effects are consistent even when participants are given control over interruptions and that these effects are robust even in an online setting where experimental control is compromised. The work presented in this thesis enhances our understanding of the factors influencing the disruptiveness of interruptions. Its primary contribution is to show that when we talk about interruptions, ‘relevance’, ‘irrelevance’ and ‘relatedness’ must be considered in the context of the contents of working memory at the moment of interruption. This finding has implications for experimental investigations of interrupted performance, efforts to under- stand the effects of interruptions in the workplace, and the development of systems that help users manage interruptions