Most of the companies I work with have projects with tasks that need to be worked by a single department, group, or individual. An example of this is a department of technical writers, or an individual with a highly specialized skill.
It is common for these single points of work effort to become bottlenecks. Contention for limited resources creates an environment where individuals are pressured to work on multiple tasks and projects at the same time.
The effect of this “multitasking” is devastating. It creates contention between managers competing for limited resources, disappointment in the performance of the resource working the task, and delays in all the tasks being multitasked.
Resources do their best by jumping from task to task trying to please everyone—yet pleasing no one. I’ve seen priorities set by who yells the loudest, offers bribes, or threatens. After time, the frustration and disappointment wear on the resources—resulting in poor performance, poor quality, or at least team disharmony.
Let’s look at the devastating effect of multitasking on the task schedule. Consider a resource that has 4 tasks, each requiring 4 hours of effort to complete. Task A, B, C, and D. Each task will be worked for 2 hours before switching to another task. Here is our sequence: A, B, C, D, A, B, C, D.
Task A is started, worked 2 hours, and then waits 6 hours as B, C, and D are worked 2 hours each. The final 2 hours for task A are worked giving a total duration of 10 hours. Although the resource was able to report that task A was started immediately, it took 2.5 times longer to complete than it should have.
Task D waits 6 hours for Tasks A, B, and C before starting. Task D is worked for 2 hours then waits another 6 hours before being worked the final 2 hours. The total effective duration for Task D is 16 hours. In this case the resource has to explain why Task D was delayed 6 hours before starting, and why it took 10 hours to complete a 4-hour task.

This simple example actually understates the problem because most tasks have preparation time that is needed to re-orient and restart the task. When included, this time adds to the total task duration each time the task is restarted.
The good news is that with proper management, multitasking can be significantly reduced, if not eliminated altogether. Doing this requires companywide task and project planning, including proper task and dependency definitions.
Got multitasking going on in your projects?