Dot Probe Stimuli/Probe Display Times


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Marguerite
Marguerite
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Hello,


I'm trying to program a dot probe study and am having some difficulties with the display times. 


For starters, is there a way to keep the probe displayed until the participants input a response?  Or, is there a way to modify the display time of the probe?  Should I be using a "stimulus timeout" command to accomplish this?  Currently I'm using the dot probe template and I'm finding that the probe disappears too quickly.



Similarly, I would like to adjust the stimuli display time so that it disappears after 500ms, instead of the preset of 1500ms. However, when I change the setting from 1500 to 500, the stimuli don't seem to appear at all.



Here is my presentation script if it helps:



<trial pleasantleft>


/ correctresponse = ("e")


/ validresponse = ("e", "i")


/ stimulustimes = [0=fixation; 500=erasefixation, pleasantleft, unpleasantright; 1500=erasewords, probeleft]


</trial>




Many thanks.


Marguerite 


Dave
Dave
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/ stimulustimes = [0=fixation; 500=erasefixation, pleasantleft, unpleasantright; 1500=erasewords, probeleft]


Here's what the above stimulustimes definition does:



  • 0 ms into the trial: display fixation

  • 500 ms into the trial: remove fixation, display pleasant and unpleasant stimuli

  • 1500 ms into the trial: remove pleasant and unpleasant words, display probe


So, the fixation duration is 500ms (0 to 500), pleasant and unpleasant stims are displayed for 1000ms (500 to 1500), probe is displayed infinitely until subject responds (1500 to ???). See the documentation for the /stimulustimes attribute for details. You should be able to take it from there.


Regards,


~Dave


Marguerite
Marguerite
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Thank you so much for your rapid response!  I see why my words weren't presenting at all.



Thanks again for your assistance.


Veronica


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