In an n-back task, the question is whether the current item matches the item shown n positions earlier. In a dual task, two streams must be tracked separately. This explains a task format; it does not establish that practicing it improves broad intelligence.
A small single-stream example
Imagine a two-back letter stream: A, B, A, C, A. The third item matches the first; the fifth matches the third. The fourth does not match the second. You must compare with the specified earlier position, not decide whether the letter has ever appeared before. That last rule belongs to a different recognition task.
What makes a task dual
A dual version could present a position and a sound together. A position match and a sound match can happen independently, so the player needs separate responses. Sound settings, presentation speed and n level all change the demands. Scores from different implementations should not be treated as interchangeable.
Choose the game actually provided
This Zehano release includes sequence recall and verbal recognition, not a full dual n-back implementation. Sequence Memory asks you to repeat an entire illuminated path. Verbal Memory asks whether a word appeared earlier in the session. Read the controls before choosing a game, and judge progress as improvement on that activity rather than a validated cognitive assessment.
Updated 10 October 2026. Original practical guide created with AI-assisted drafting and software checks. No professional or clinical review is claimed. Editorial approach and corrections.