Before reading this, you really should first check out the regular Corsi task.

The Corsi task is a test of your working memory. Here we only focus on the differences between the regular Corsi task and the backward test (the regular Corsi task can be called a forward memory span test, in analogy to the forward digit span test).

The term working memory is here used because the participant needs to actually manipulate the contents of the short-term memory during the recall process. For a review see, for example Diamond, 2012

In both tasks, you need to remember the order in which a number of rectangles highlight. In the backward test, you need to click (or touch) the rectangles in reverse order. That is, you need to start with the one you saw highlighted last.

In the digit span test, there is also a forward and a backward version. Similarly, we have the same for the Corsi test.

The backward version of the Corsi test was, to the best of my knowledge, first used in a study in 1989 (Isaacs & Vargha-Khadem, 1989), and in more detail tested by Kessels and colleagues (2008).

This task was originally not designed as a computer task.

The block span or Corsi span is defined as the longest sequence a participant can correctly repeat. Similarly, we have a backward Corsi span, which is the longest sequence in the backward Corsi test.
The normal (average) score is around 6. The highest possible block span in this task is 9. In principle, there might be people who can do better, but that will be quite rare.

About this implementation

  • In this implementation, we start with a sequence of 2 blocks

  • Once the sequence has been shown, you hear the word "go" (if you have your speakers on)

  • You need to click with the mouse the blocks in the reverse order as shown before

  • When you are done, you click the green block "done"

  • You get feedback (smiley face means you did it correct, or frowny face if you made a mistake)

  • If you do it correctly, you go the the next higher number of blocks

  • If you do it wrong, you get once more chance. If you do it then wrong again, you get your score (the backward Corsi block span)

Run the demo

In this example, you will carry out the backward Corsi task. You will see further instructions. You need a mouse and ideally you would have sound speakers (because after the sequence is shown, a voice will say "go"). But even without sound, it is fairly obvious when the sequence ends and when you need to start.

Data output file

You do not need this information, unless you want to understand the output data file. You can ignore this if you just want to find out your own score. This is only necessary if you want to carry out the experiment with multiple participants.
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


The highest Corsi backward span so far


The number of items in the current trial to be remembered (starting with 2)


Status of current trial (1=correct, 0=wrong)


The table row from the table (this experiment comes with 500 random block arrangements and sequences)


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

  • Corsi, P.M. (1972). Human memory and the medial temporal region of the brain. Doctoral Thesis at McGill University (Canada). Download from here. (in the search box, type "Corsi")

  • Isaacs, E. B. and Vargha‐Khadem, F. (1989), Differential course of development of spatial and verbal memory span: A normative study. British Journal of Developmental Psychology, 7: 377-380. Link here

  • Kessels, R. P. C., van den Berg, E., Ruis, C., & Brands, A. M. A. (2008). The Backward Span of the Corsi Block-Tapping Task and Its Association With the WAIS-III Digit Span. Assessment, 15(4), 426–434. Link here