Dual N-Back is the gold-standard brain-training exercise used in neuroscience research. It simultaneously challenges two channels of your working memory:
A square lights up in a 3×3 grid. You need to remember where it appeared.
A letter is spoken aloud. You need to remember which letter you heard.
Each turn, a new position and sound are presented simultaneously. Your task is to decide whether the current position or sound matches the one from N turns ago.
The "N" is how far back you compare. In 2-back, you compare each turn with 2 turns ago. In 3-back, you compare with 3 turns ago. The higher the N, the harder it gets!