Interruption and multitasking are fundamental sources of error, that probably have a common mechanism in the brain's function as a sequntial processor. Both require switching; sequential processing means that we truly cannot multi task as far as attention is concerned. Attention in task performance is like a spot light - it can only shine on one part of a task at a time.

Interruption is an externally and culturally aligned behavior characteristic of the cultural norms established in a clinical area. It is likely influenced by relationships; for instance are you more or less likely to interrupt a friend in the middle of a task as compared with someone you don't really know? Hierarchy probably has an effect too; would you be more or less likely to interrupt someone who you perceive is lower on the hierarchy? What about patients and family; do they know when and how to get your attention safely? Do they know when you are involved in something and should not be interrupted?

Recently a friend shared an incident in which a breast milk administration error occurred even though this NICU uses a bar-code process. Upon review of the circumstance, interruption was probably a key contributing factor. The nurse was interrupted during the process and returned to complete it, missing the code scan which would have detected the wrong milk. This had become a well entrained task, repeated correctly many times, but with attention diverted the switch back to the task resulted in error.

John Medina's latest book includes this and many other little-known facts about how the brain works based on his years of working in the field. He also has a blog and a few entries on YouTube.