Spacebar skip — press Space any time a number is on screen to dismiss it early instead of waiting it out. Doesn't affect scoring or the pace of the digits, it just gets you past the number faster — handy on no-go trials once you've already decided nothing needs pressing.

N-back mode — instead of pairing each digit with the one spoken right before it, pair it with the digit from 2 digits back. Everything else works the same: judge the flashed number against that sum.

Works with dichotic attention switching too — the sequence carries across ear switches, so a higher level stays trackable even as the voice changes.

Dichotic attention switching (experimental) — every interval, two different digits now play at once, one in each ear. A short beep in one ear tells you which ear to follow. Add and judge digits from that ear only, and let the other ear pass by unattended — until the beep plays in the other ear.

The two ears also speak in different voices — male in the left ear, female in the right ear — as a constant cue for which stream is which, on top of the beep.

• A beep in your left ear → follow the left ear from then on.
• A beep in your right ear → follow the right ear from then on.
• The target keeps switching every few trials with no warning besides that beep, so listen for it.
• Your running addition carries across the switch — keep adding onto the same sequence, just from the newly-cued ear.

Needs stereo headphones — the two streams won't separate on a single mono speaker. The beep uses the beep volume setting below.