Dual N-Back exercise is a scientifically proven way of improving your fluid intelligence. Fluid intelligence refers to the ability to reason and to solve new problems independently of previously acquired knowledge. More information about the science from the support page.

The idea is to remember sequentially spoken letters and positions of a square. The sequence length is increased or lowered for the next round depending how well you are doing.

You will advance to your current top performance level quite fast and it takes some persistence to get to the next level. On the other hand, the length of the sequence (i.e. difficult level) for each round is deliberately changed quite easily so that there is minimal change to develop automatic processes and task-specific strategies which are actually not increasing your fluid intelligence in the long run.