**UPDATED POST**: my friend Steve Chew sent me information about this task switching demonstration, so I’m updating this post to include two versions (thanks Steve!)

This demonstration is a fast, foolproof way to help students and teachers experience the cost of switching between cognitive tasks. Even when it feels effortless and instant, interrupting a task costs us time and cognitive effort, even if it “just takes a second.”

**VERSION #1**: I found this activity on the fabulous The Learning Scientists blog (here’s a google doc version). The demonstration has a few steps:

- Ask students to get out their phones and get to the stopwatch app (or pair students up and have them time each other on the tasks).
- Task 1 = “Count as quickly as you can from 1 through 26. Try to time exactly how long it takes you – feel free to do this 2-3 times to make sure you get an accurate time. Write down your best time”
- Task 2 = “Recite the alphabet from A to Z as quickly as you can. Again: try to time yourself precisely. Write down your best time.”
- Task 3 = “Now you’re going to alternate those two tasks – counting from 1 to 26 and saying the alphabet. This will sound like ‘1, A, 2, B, 3, C, etc.’ Concentrate, don’t give up, and make sure you get all the way to 26 and Z! Time yourself and write down your time.”
- Note: alternatively, on each of the three tasks you can as students to average their times across a few trials – good data collection practice, and a review of measures of central tendency!

It will be obvious to everyone that task 3 is difficult! Try to encourage everyone to persevere and finish task 3 – switching between task 1 and task 2 takes cognitive effort and many people will be tempted to give up.

You may want to collect the times on each task and average the times in order to compare those data with the graph at the top of the page from the Learning Scientists blog. But even before you analyze the data, everyone will notice that task 3 tasks much more than double the amount of time than task 1 and task 2.

You may want to use this experience to start a discussion about why task 3 takes so much more time than task 1 and 2 combined. Teachers and students may already understand that the term “multitasking” is problematic: we can’t selectively attend to more than one cognitive task at a time in our working memory. Some people think they are better or worse multitaskers, but it’s more accurate to think about “task switching:” some of us may be faster at switching between tasks than other people.

But no matter how quickly we learn to switch between tasks, there is always a cost! During task 3, we have to switch between task 1 and and 2. Each of those “switches” takes a very short time, and then switching back takes another additional short amount of time. Adding up all the time it takes to make those “micro-switches” each time explains why task 3 takes so much time and why it takes so much cognitive effort. By themselves, tasks 1 and 2 are simple, like many of the cognitive tasks we do daily. It’s incredibly tempting to leave one of these simple tasks “just for a moment” to get another simple task done immediately. While I was writing this paragraph, I saw a zoom notification on my phone that a school principal wanted help finding a report online, so I switched from my laptop to send her a quick email. The irony of switching tasks while writing a blog about task switching exemplifies how tempting task switching is. It’s often unavoidable, but acknowledging the cost is important. Teachers can help students realize that switching their attention to their phone , even just for a moment, has a real cost in time and cognitive effort. That realization might help us resist some of these task switching temptations.

**VERSION #2:** I like the simplicity of the 1-26/A-Z version but this similar activity might also be useful (thanks to Pat. O’Meara for finding this one! Adapted from this video: Try the Myth of Multitasking Exercise!)

- Get out a sheet of paper and draw three lines across it horizontally so that it looks like this:
- Tell students you’re going to time how long it takes us as a group to write the phrase “Task switching steals time” in the top row. Turn your paper over when you are done. Ready, Go!
- Write about how long it took the class on the board (doesn’t need to be exact).
- Next task: in the next row, write the numbers 1 through 23. Turn your paper over when you are done. Ready, Go!
- Write about how long it took the class on the board (doesn’t need to be exact).
- In the 3rd and 4th rows, you are going to alternate between letters and numbers. In the 3rd row, you are going to write the same phrase one letter at a time. After you write the S in the 3rd row, you will write a 1 in the 4th row. You may want to demonstrate this for them on the board. Keep doing that until you are done writing all the letters in the phrase in the 3rd row and the numbers 1-23 in the 4th row. Write legibly! Ready, Go!
- Write about how long it took the group on the board (doesn’t need to be exact) – this last task will take them significantly longer!

**VERSION #3:** Steve chew figured out that this one is the original version! Steve found out that David Meyer (U. Michigan) developed this activity and used it in his classes around 2008. Dr. Meyer’s version is similar to version 1 above, but is more concise:

- Partner students up, one time keeping and one participating, then switch roles
- Task 1 = count from 1 to 10, then immediately say the alphabet out loud from A-J
- Task 2 = alternate between counting and the alphabet – e.g. 1-A, 2-B. etc.
- Data analysis: divide the time for task 2 by task 1.
- Ask students how many have a ratio of less than 1 (meaning that task 1 took more time than task 2) – there won’t be any!
- Gather some “ratio” data from students (either from all students or a sample of students, anonymously if needed). Point out that if a ratio is 2, that means it took 2 times as long to do task 2 than task 1. That is the cost of task switching!

Steve included this graphic from Dr. Meyer’s class, which might be a great way to extend this demonstration into a discussion of the cost of task switching during studying!

UPDATE: Peps McCrea discussed the cost of task switching in his most recent “evidence snacks” email newsletter: “Interruptions Leave a Wake.” He shares this article at the end – useful research about the task-switching cost of classroom interruptions by announcement over the intercom, etc. Thanks Peps!