Nback

The n-back task is a continuous performance measure used to assess working memory. In a typical version, a sequence of stimuli is presented (visual items such as letters or shapes, or spatial locations; or auditory items). The participant must indicate whether the current stimulus matches the one presented n items earlier in the sequence. The value of n defines the difficulty (1-back, 2-back, 3-back, etc.). For example, in a 2-back task, a target occurs when the current item is the same as the item two steps back.

Variants differ by modality, response type, and whether responses are required for matches, non-matches, or both. Computerized implementations often use adaptive algorithms that adjust n to maintain performance around a predefined accuracy level. Performance is typically summarized by accuracy and reaction time, or by signal-detection measures such as d'.

Neuroscientific studies show that n-back engages a frontoparietal network involved in working memory updating and maintenance, including the dorsolateral prefrontal cortex and posterior parietal regions. Activation generally increases with higher n, though findings vary with task design and modality.

It is widely used in cognitive psychology and neuroscience to study working memory, attention, and cognitive control in both healthy individuals and clinical populations (e.g., ADHD, schizophrenia). In training research, some studies report improvements on n-back performance and near transfer to similar tasks, but evidence for far transfer to general intelligence or daily functioning is inconsistent. Methodological differences and publication bias contribute to mixed conclusions on training efficacy.

Limitations include task-specific strategies, modality effects, and variability in results across studies. As a result, n-back remains a useful probe of working memory capacity and updating, rather than a definitive measure of overall intelligence or cognitive health.