In 2013 I reported how a 3-second interruption while doing a task doubled the rate of sequence errors, while a 4s one tripled it. A new study has attempted to measure just how much ongoing interruptions can negatively affect the quality of a complex creative task.
The study involved 54 students who were given 12 minutes to outline and 12 minutes to write a short essay on an assigned topic. One group was interrupted multiple times with an unrelated task during outlining, while another group was interrupted repeatedly during the writing stage, and a control group had no interruptions.
The quality of the essay produced was significantly lower in both interruption conditions (an average score of 3.06 for the writing-interruption group, and 3.13 for the outline-interruption group, compared to 3.71 for the control group). The number of words produced was significantly lower when the student was interrupted during writing (282 words vs the control group's 315 words), but not when interrupted during outlining (307 words).
Essay quality was assessed by independent graders using a 6-point scale. The interruptions occurred every three minutes and lasted one minute, during which the student was asked to complete an arithmetic problem or word puzzle (this time wasn't included in the 12 minutes).
A follow-up experiment in which the time given was lengthened to 20 minutes, and interruptions occurred at random intervals, produced similar results, although the overall scores were slightly higher.
 . Do Interruptions Affect Quality of Work?. Human Factors: The Journal of the Human Factors and Ergonomics Society [Internet]. 2014 ;56(7):1262 - 1271. Available from: http://hfs.sagepub.com/content/56/7/1262