About m-back: m-back is a mobile version of the well-known dual n-back brain training exercise. Recent studies showed that practicing a dual n-back task can expand your working memory and increase your fluid intelligence (for more information see http://en.wikipedia.org/wiki/N-back).
The task: You are presented with two independent sequences of stimuli simultaneously. The task consists of indicating when a current stimulus matches the one from n steps earlier in the sequence. The parameter n can be adjusted to make the task more or less difficult.
This version: This version of dual n-back requires you remembering a sequence of colors and a sequence of positions at the same time. For this purpose you are confronted with a sequence of colored squares in a 3x3 grid. If you identify a color or position match (that means the color or position of the current square already appeared n steps before), you have to touch the current square to get the advantage. Otherwise you get a disadvantage.