I have come across a certain problem which I cannot solve on my own.
I would like to create a task where participants are presented two kinds of shapes (i.e. primary-task stimuli) and are supposed to press certain keys depending on the type of stimuli they see (e.g. ‘a’ key for circle and ‘l’ key for square). However in 25% of trials after the presentation of the primary-task stimulus an auditory stimulus (stop-signal) appears and the participants are supposed to withhold their reaction. And here comes the problematic issue: the interval between the primary-task stimulus and the stop-signal is initially set at 250 msec and should be adjusted continuously with a staircase tracking procedure: when inhibition is successful, the interval increases by 50 msec; when inhibition is unsuccessful, the interval decreases by 50 msec.
Is there any possibility to create such a conditon (i.e. the variable onset of an auditory stimulus depending on participant’s input in randomized 25% of trials) and if so, how can I do it? I’d be happy with any help.