Implement a stop-signal delay in the stop-signal task

frederic

Hello all,

Even with your advices, I can't insert an SSD to the stopsignal task example. It works when the answer of stop trial is a mistake and the SSD decrease of -50 but when the answer is correct (none) nothing happened: no increase of 50 ms.

https://forum.cogsci.nl/uploads/editor/d7/kf2tcp65uc1w.jpg

https://forum.cogsci.nl/uploads/editor/t6/zi56guc90uvm.png

https://forum.cogsci.nl/uploads/editor/ln/e80y8tfhrpru.png

https://forum.cogsci.nl/uploads/editor/fi/14znuuueq9gf.png

Thanks for your help
Frédéric

knmeyer

Hi Frederic,

It looks like you're using not the response to the stop signal, but what you specify in the loop initially. Right now, those are entirely colinear, such that every time you specify correct_response = None, also stop_signal = A. This means that when you specify "if var.correct_response = None and var.stop_signal = " "" that never happens. My understanding would be that for a stop signal task, you would want to decrease the duration (SSD) when they appropriately stopped themselves and increase the duration if they were supposed to stop and then they did not. Let me know if I'm misunderstanding. Based on that, though, the code below should work:

#when participants should stop (i.e. stop trial), and they do stop (i.e. no response), decrease SSD.
if var.correct_response == None and var.SSD > 99 and var.response == None:
        var.SSD -= 50
#when participants should stop, and they do NOT stop (any response), increase SSD.
if var.correct_response == None and var.response != None:
        var.SSD += 50

Best,
Kristin