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Interruptions and short-term memory

Key Points

  • Interruptions tax people's short term memory. This makes errors more likely to occur.
  • If you give yourself a few extra moments to recall what you were doing before you were interrupted your memory is more accurate.
  • Visual cues put less strain on your short term memory and make resuming after interruptions easier and less error prone.

Short term memory
As you go about your work, checking emails, taking phone calls and having meetings, you have to keep track of lots of things. To get stuff done you have to keep track of what you're doing now, what you've already done and what you need to do next. You store this information in your short term memory, which acts like a to-do list.

We are often interrupted in our day-to-day lives. Interruptions make things more difficult for our short term memory because they disrupt things being kept there. Switching between lots of activities makes it harder to keep that mental to-do list organized and up to date. When we are interrupted we often, by mistake, mentally tick-off items that we haven't completed or fail to tick-off items that we have. These kinds of errors are often a hassle but on hospital wards or in cockpits they can endanger lives.

Why are interruptions disruptive?
People regularly interrupt themselves when doing tasks. CHI+MED researchers have shown that constantly switching from one task to another can lead to errors. This happens because of the way actions are strung together when we complete activities. For instance, putting a kettle on cues us to get mugs out of the cupboard. Getting mugs out cues us to fetch tea bags.

If we focus on one task this chain of steps helps us to avoid errors. But if we are constantly interrupting our tea making to check how our pasta and bolognese are doing, we can inadvertently break the chain of steps. This makes it harder to remember what we're doing and makes us more likely to do silly things like putting teabags in the saucepan instead of the teapot. The same applies in hospitals when a nurse is doing something more serious like setting up a series of machines to give a patient drugs.

Stopping errors
Is there anything we can do to help people avoid making errors when they are interrupted?

One way we can stop errors is to reduce our reliance on our short term memories. Rather than have to store that to-do list in our heads we can make visual reminders. Then if our memory fails us we'll still be able to resume our task in the correct place. Our research has shown that carefully designed visual cues can be used to help people remember what they need to do in a task after they have been interrupted.

It's not always possible to have cues though. In busy and complicated environments like hospital wards people have to rely on these mental to-do lists. Our research has shown that taking an extra moment to think about what you're about to do after interruption reduces the likelihood of making errors. This is because the longer you spend trying to recall something the more likely you are to able to retrieve it from short term memory. Think of the tip-of-the-tongue effect, that thing that occurs when the word you want to use is on the tip-of-your-tongue but momentarily just won't come to mind. Sometimes a bit of extra mental effort allows you to remember something that a moment ago you couldn't quite recall. Our research has shown that the same process can make resuming after interruptions less error-prone.

Key people
Sandy Gould and Anna Cox (UCL)

Publications
Back, J., Cox, A., & Brumby, D. P. (2012). Choosing to interleave: human error and information access cost. In Proceedings of the 2012 ACM annual conference on Human Factors in Computing Systems (pp. 1651–1654). New York, NY, USA: ACM.

Brumby, D. P., Cox, A. L., Back, J., & Gould, S. J. J. (2013). Recovering from an interruption: Investigating speed-accuracy trade-offs in task resumption behavior. Journal of Experimental Psychology: Applied, 19(2), 95–107. doi:10.1037/a0032696

Gould, S. J. J., Brumby, D. P., & Cox, A. L. (2013). What does it mean for an interruption to be relevant? An investigation of relevance as a memory effect. Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 57(1), 149–153.

Jones, S. A., Gould, S. J. J., & Cox, A. L. (2012). Snookered by an interruption?: use a cue. In Proceedings of the 26th Annual BCS Interaction Specialist Group Conference on People and Computers (pp. 251–256). Swinton, UK, UK: British Computer Society.