Introduction
The difficulty of rapidly switching between two different tasks was first reported by Jersild in 1927, but it was not until the mid-1990s that the task-switching paradigm became popular with cognitive psychologists and neuroscientists. The paradigm’s popularity has probably to do with the fact that task-switching paradigms are so surprisingly difficult.
Jersild had people doing one task at the time and compared that to people doing two tasks in rapid alternation. He found that people perform more slowly when they are alternating between tasks. Apparently, the act of switching requires special mental operations, and the task-switching paradigm is designed to investigate the nature of these operations.
Robert Rogers' and Stephen Monsell’s 1995 paper has contributed massively to the popularity of task-switching paradigms. Their alternative runs approach (demonstrated below) was different from Jersild’s paradigm.
In this task, participants carry out two trials of task A, followed by two trails of task B, and then back to task A. Hence, a task switch occurs every two trials. The difficulty to switch between tasks is expressed as the slow down immediately following a task switch. That said, this paradigm also allows to express the cost Jersild measures. In Jersild’s time (before computers), the task-switch cost was practically difficult to measure.
Today, we know that people cannot overcome the difficulty of switching even with fairly long training (Stoet and Snyder, 2007). Surprisingly, though, Stoet and Snyder (2003) showed that monkeys can (given sufficient training).
About this implementation
This example is very close to Roger and Monsell’s paradigm. In this example, you need to respond to number and letter combinations. Follow the detailed instructions on screen. At the end of the tasks, you will get feedback about exactly how fast you are when you do just one task at the time ("pure blocks"), and how fast you are when you are doing two tasks mixed. In the mixed block, we distinguish between "task-repeat trials", namely the trials in which you do the same task as in the trial before. And then there are "task-switch trials", trials in which you switch from doing one task to doing another task.
This demo takes less than 5 minutes to complete. In the laboratory, these tasks last longer to get a more reliable estimate of one’s speed, though.
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Note, you can show your response times and copy and paste them to a local file for your own data analysis.
Run the demo
| In this experiment, you respond with the keys b and n to letters (in the consonant/vowel task) and numbers (in the odd/even task). The instructions are all on screen and require some concentrated reading. |
| This is a very difficult task! You need to remember the rules of two different tasks and you need to frequently switch between them. In the cognitive laboratory, this is one of the more difficult tasks. Are you up to it? |
Data output file
TODO
| In PsyToolkit, the data output file is simply a textfile. The save line of the PsyToolkit experiment script determines what is being saved in the data output file. Typically, for each experimental trial, you would have exactly one line in your text file, and each number/word on that line gives you the information you need for your data analysis, such as the condition, response speed, and whether an error was made. |
Meaning of the columns in the output datafile. You need this information for your data analysis.
| Colum | Meaning |
|---|---|
1 |
blockname |
2 |
position of stimulus 1,2,3,4 (top left, top right, bottom right, bottom left |
3 |
tasktype (1 or 2) |
4 |
the letter stimulus |
5 |
the number stimulus |
6 |
type of block (1=just task 1; 2=just task 2; 0=both tasks mixed) |
7 |
1=task switch , 0=task repeat |
8 |
status (1=correct, 2=error, 3=too slow) |
9 |
response time (ms) |
10 |
total time (response time + button release time) |
| The response time is when people press down the button. But it also takes some time to "release" the button again (to go up). For analysis, I recommend to use the response time. |
Download
| If you have a PsyToolkit account, you can upload the zipfile directly to your PsyToolkit account. Watch a video on how to do that. If you want to upload the zipfile into your PsyToolkit account, make sure the file is not automatically uncompressed (some browsers, especially Mac Safari, by default uncompress zip files). Read here how to easily deal with this. |
Further reading
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Jersild, A.T. (1927). Mental set and shift. Archives of Psychology, 89, 5–82.
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Monsell, S. (2003). Task switching. Trends in Cognitive Sciences, 7, 134-140.
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Stoet, G. & Snyder, L.H. (2003). Executive control and task-switching in monkeys. )Neuropsychologia, 41_, 1357-1364.
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Stoet, G. & Snyder, L.H. (2007). Extensive practice does not eliminate human switch costs. Cognitive, Affective, & Behavioral Neuroscience, 7, 192-197.
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Vandierendonck, A, Liefooghe, B, & Verbruggen,F. (2010). Task Switching: Interplay of Reconfiguration and Interference Control. Psychological Bulletin, 136, 601-626.