repeat trial once max

Hi, all,
I am building a stop-signal task in which I want to limit stop trials to be presented only once or two in a row maximum but no more.

So - go, stop, stop, go, stop, go

but not - go, stop, stop, stop, go

I tried to solve this by using a stop counter that increments to 1 every time a stop trial is presented, and then this parameter is reset every time a go trial is presented, and under trial rules choosing present only when stop counter is <2.

The problem is that this will not allow the stop trial to be presented at the end of a given block in which the third and second to the last trials are stop, stop.

I think I’ve worked around this problem by specifying a second rule for stop trials (attached). There are 64 trials total, 16 stop trials and 48 go trials.

For stop trials, present trial only if the following criteria are met:

Parameter “Stop counter” <2 OR
Number of times this trial has been presented <16 AND
Number of trials presented in block = 63

This seems like it should work, but testing is difficult since presentation of two stop trials at the third and second to last trials in a block happens infrequently.

Can anyone weigh in to let me know that this should work or alternative solutions?

Untitled.pdf (142 KB)

James, this would be faster addressed over the phone. Please call me at 1-310-548-9595.