TEST

Verbal working memory · Numerical 2-Back

Maintenance and updating under high load

Ability to keep several items in mind at the same time and update them. Detects difficulties following conversations, multi-step instructions, or demanding intellectual work.

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N–2

LOAD

1–9

DIGITS

High

COGNITIVE LOAD

Verbal

MODALITY

WHAT THE TEST IS

Does it match the one from two positions back?

N-Back task with high load. The user must press the space bar when the number they see matches the one shown two trials earlier (n–2). Digits from 1 to 9 appear sequentially.

It requires keeping two items in mind at the same time and updating them on each trial: discarding the oldest one, keeping the penultimate and current items, and comparing them. It places high demands on executive control and working memory (Perlstein et al., 2004).

HOW IT IS ADMINISTERED

Compare the current number with the one from two positions back

The user sees numbers from 1 to 9 appear and must press only when the current number matches the one shown two trials earlier. On each turn, they must discard old information, keep the penultimate item, and compare it with the current one. This is the classic high-load version of working memory.

WHAT THE TEST MEASURES

Indicators and their interpretation

Correct responses

n–2 matches correctly detected. Reflects the ability to manipulate verbal information under high executive load.

High: effective manipulation and adequate updating.
Low: limitations in high-load working memory.

Omissions

Matches that were not responded to. Sustained attention and vigilance under high demand.

High: updating failures, cognitive fatigue.
Low: effective monitoring under load.

False alarms

False detection of a match. Especially sensitive under high load: confusion with n–1 or n–3.

High: difficulties keeping the sequence active and accurate.
Low: accurate discrimination.

RT in correct responses

Speed of updating under high-load conditions.

Slow: manipulation difficulty, hesitation.
Fast: efficient manipulation.

RT variability

Attentional stability under high load.

High: fluctuations, fatigue.
Low: sustained processing.

RT fatigue

Change in RT between the final and initial 25%.

High: accumulated executive fatigue.
Low: resistance to cognitive effort.

REFERENCES

Bibliography

Perlstein, W. M., Cole, M. A., Demery, J. A., Seignourel, P. J., Dixit, N. K., Larson, M. J., & Briggs, R. W. (2004). Parametric manipulation of working memory load in traumatic brain injury. Journal of the International Neuropsychological Society.

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