The Boston Globe today had an interesting tidbit in their Uncommon Knowledge column, under "When not to interrupt." They reference a recent article from Motivation and Emotion, "Don’t interrupt me! Task interruption depletes the self’s limited resources" by Nicholas Freeman and Mark Muraven (Vol 34, No 3, pp 230-241).
The short version is that while we have known that it takes a while to switch between (incomplete) tasks, the research suggests that the actual work quality on the second task is impacted by when the first task is interrupted. Specifically, if the first task is nearly done, the second task quality suffers significantly. The assumption is that there is a lot of mental attention still left on the almost-completed work, and that detracts from the ability to do the new work.
Here's the abstract (have to buy the article or track down the journal for the full text):
It is a common occurrence in daily life to be interrupted prior to completing a task. Such interruptions may have deleterious effects for limited self-resources, especially if they occur just prior to task completion. This hypothesis was tested in three experiments. In the first two, participants initially engaged in a card sorting task, and then subsequently performed a self-control task. In Experiment 3, participants first engaged in a word search task and then worked on an executive function task. In all instances, participants who were interrupted just prior to attaining their goal of completing the initial task, but not those who were stopped earlier in the task or who were allowed to finish, showed evidence of impairment on the subsequent measures. The findings suggest that the desire to pursue a goal increases as goal attainment draws nearer, and that the amount of self-control needed to stop working on a task is modified by situational variables such as goal distance.
I'll say it again. Focus on doing one thing at a time. This one brings in a new twist: If you have to break up a job for some reason, find good stopping points. And by all means, if you are nearly done, just finish it already!
[Photo: "A Time For Everything" by Mike]