NBack Task – Touchscreen

Background

The N-back task is a continuous go/nogo performance test to measure working memory. It primarily tests executive functions, specifically the ability to monitor, update, and temporarily store information. Participants view a fast sequence of stimuli (e.g., pictures) and must indicate if the current item matches the one presented N steps earlier in the series (the go 'targets'). The higher N is, the more difficult the task becomes. The Millisecond 'NBack Task – Touchscreen' is inspired by the One-Back (OBK) Task of the Cogstate Brief Battery (CBB), and its implementation is based on the published description of the task by Paul Maruff and colleagues in 2009.

The One Back (OBK) task of the Cogstate Brief Battery is a rapid-fire digital test designed to measure working memory and attention. In addition to the OCL, the Millisecond library also provides implementations of the CBB's 'Detection Task', the 'Identification Task', and 'The One-Card Learning Task'. All Millisecond implementations are based on publicly available information (e.g. Maruff et al, 2009). All tasks of the CBB use a similar card-game user interface and are designed to run on touchscreens. Nevertheless, Millisecond's implementations will adapt to mouse-use on non-touchscreens.

Task Procedure

Participants learn about the n-back task in a brief tutorial that includes a short practice. In addition, the entire tutorial can be repeated as often as necessary before starting the test phase.

The interface of the n-back task consists of a 'deck' of cards presented in the center of the screen, a 'YES' and a 'NO' response button as well as a circle-shaped home button on which the response finger rests until a card is turned over. The home button is implemented to ensure that response fingers are roughly equally distanced from the 'YES'/'NO' response buttons for each trial. Once a card is turned over, participants are asked to press the 'YES' response button as fast as possible if the current back is the same as the one n trials before it. If the current card is not the same as the one n-trials before it, they are instructed to press the 'NO' button as fast as possible. After the response is made, a card-animation is started that 'returns' the card back to the stack.

The Millisecond 'NBack Task – Touchscreen' implementation provides 52 possible cards to play with but currently restricts the number to the set of 13 club cards. A larger selection pool makes the n-back task less challenging as random repeats of nontarget cards (in nontarget positions) are less likely to happen; thus any repeated cards have a high chance of being a target (this would negatively affect particularly higher n-back procedures). In addition, using the same suit forces participants to pay close attention to the actual cards presented.

By default settings, the Millisecond 'NBack Task – Touchscreen' runs a one-back procedure with one testblock that runs 42 trials (+ one start trial). Half the trials present a target. The order of target and non-target trials is randomly determined. Each new card presentation is initiated by the pressing of the home button. After a random delay of 500-1500ms, a card is uncovered and left open for 2000ms during which the participants must decide to press the YES or NO button. If a response is made, the response button is highlighted and the 1-second card returning animation is started. If no response is given withing the response timeout, the card returning animation is run regardless and a new trial can start.

What it Measures

N-back tasks measure working memory

Psychological domains

• Working Memory: Storing and updating short term memory
• Inhibition: Suppressing responses to familiar items that do not match the n-back rule
• Sustained Attention: Maintaining focus over a repetitive series of trials without 'drifting'

Main Performance Metrics

• Accuracy Measure: raw and arcsine converted proportion correct; main measure of recognition success
• Response Time: mean (raw and log10 transformed) and median correct response times (in ms) to stimulus presentation; main measure of decision-making speed

Psychiatric Conditions

The following patient groups have been tested with the OBK

• Mild Cognitive Impairment (MCI)
• Alzheimer’s Disease (AD)
• Parkinson’s Disease (PD)
• Schizophrenia
• Traumatic Brain Injury (TBI)

References

Search Google Scholar for peer-reviewed, published research using the Inquisit NBack Task – Touchscreen.

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Maruff P, Thomas E, Cysique L, Brew B, Collie A, Snyder P, Pietrzak RH. Validity of the CogState brief battery: relationship to standardized tests and sensitivity to cognitive impairment in mild traumatic brain injury, schizophrenia, and AIDS dementia complex. Arch Clin Neuropsychol. 2009 Mar;24(2):165-78. doi: 10.1093/arclin/acp010. Epub 2009 Mar 25. PMID: 19395350.