When One Becomes Two
Two tones, one rhythm, no tricks. WIZ finds the pitch gap where a single galloping sound splits into two separate ones, and the band in between where what you try to hear is what you hear.
Two tones, one low and one high, repeating forever in the pattern low high low rest. That is the entire stimulus. Nothing else happens, nothing is hidden in it, and it never changes during a trial.
Put headphones on if you have them. Then press both buttons and listen for how many things are playing.
The gallop in the second one is not quiet. It is gone. You can know the rhythm is still there, count it on your fingers, and still be unable to hear it. Somewhere between those two settings your hearing switches from one thing to two, and the interesting part is that it is not a line. It is a band, and inside it what you are trying to hear decides what you get.
Sixteen short trials find both edges of your band. Then one longer sequence, parked inside it, shows you the part nobody expects: it falls apart on its own while you sit still.