Continuous Performance Task

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A Continuous Performance Task/Test, or CPT, is a psychological test that consists of a series of stimuli. It is often used as part of a battery of tests to try to understand a person's capacity to sort and manage information. As such, the test can be useful as part of a battery to understand a person's 'intelligence quotient', 'working memory' and their 'executive function'. It is important to understand that such a test cannot be taken on its own as an indication of any particular feature of the human mind, but only as part of a constellation of tests - and their interpretations in the light of one another. The test has proved very useful for scientists working in brain mapping, who seek to identify which parts of the brain are primarily involved in working memory and information processing. 1

In a test like this, the subject (or patient, in a clinical setting) is told that they will see or hear a series of letters or numbers (occasionally symbols), one at a time - this series will vary in length, hence 'n'. It could have two elements, or three, or four, etc. They are then read a series of other letters or numbers, and are asked to state whether the 'new' data fits in with the 'back' data. So, did the new letter occur in the original group of letters? In the visual version of the test, they might be asked if the symbol appeared in the same place as previously. Brain mappers use visual tests with push button responses, as the head must be kept completely still in order for the imaging machinery (which is focused on the brain) to function correctly. Thus they avoid any test which requires the subject to speak, as the movement of the jaw and the muscles that control it would spoil the image.

The simplest version of the test involves the presentation of a digit or letter on its own, and the participant is asked to recall the previously displayed digit, when the presently displayed digit disappears. Thus the participant is trying to think 'one back'. Over the course of the test, the examiner may add to the initial group of letters (thereby increasing the 'n' of the original set). The examiner will be looking to see how far 'back' into the group of letters the subject can recall, as the 'n' of letters increases - thus the subject is asked to recall 'n-back'.

Examples of N-back task

  • 1-back
A G T T S T S S A G T G G S
Y Y Y


  • 2-back
A G T T S T S S A G T G G S
Y Y Y


  • 3-back
A G T T S T S S A G T G G S
Y Y Y

1 Adrian M. Owen, Kathryn M. McMillan, Angela R. Laird, and Ed Bullmore4, Human Brain Mapping 25:46 –59(2005).

Other CPTs

1 Adrian M. Owen, Kathryn M. McMillan, Angela R. Laird, and Ed Bullmore4, Human Brain Mapping 25:46 –59(2005).


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