This 2G DNB game is a powerful brain training combination of the 1G (output gated) DNB and the input gated DNB. Once you’ve understood how to play each of these games individually it is easy to understand the logic of playing the 2G DNB game. You have to both filter which two streams of stimulus you attend to (orange/lime vs letters/numbers), and then logic-gate your responses (OR, AND, XOR)!
Let’s look at the examples above. In the first example, the two dots (OR gate) tell us that it is just the standard dual n-back, where in the upper panel example you have to attend to the lime disk and audio letters (ignoring the orange disk and numbers). You respond if there is a simultaneous disk+letter 2-back match, as well as if either the disk or the letter is a match on its own. The response keys (F and L) for n-back matches are shown in grey below. In the lower panel example, you have to attend to the orange disk and its number (ignoring the lime disk and the audio letters). You can see that even though the stimuli are exactly the same in both upper and lower panels, correct matches are different depending on the pair of stimuli you are attending to.
In the second example the two dots with a dividing line (XOR gate) tell us that you can respond for an n-back match if there are EITHER disk location OR letter/number matches, but not both together. This type of XOR response is explained here. In the upper panel example, you are only attending to the lime disk and audio letters. In the bottom panel example, you are only attending to the orange disk and its number.
In the third example the equals sign (AND gate) tells us that you can respond for an n-back match if BOTH the disk location AND the letter/number match at the same time, but not if either of them is a match on its own. In the upper panel example, you are only attending to the lime disk and audio letters. In the bottom panel example, you are only attending to the orange disk and its number.