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Tracking exact onset/offset time of stimuli


I am building an experiment that presents a series of images starting at 4 seconds, in 4 seconds in duration, with participants being asked to make a keyboard response to the image within this time period. Between each trial, I have a fixation cross that is presented for 2 seconds, in between two blank screens that are presented for 1 sec each.

In the builder view I have set it so that the image should show for 4 seconds, but I want to track in the output file exactly how long the image was presented for. The trial does not end with the keyboard response, but should always end after being presented for 4 seconds. However, what shows up for me right now is only the start time for each image, while the image.stopped is always recorded as “None” in the output file. This is not an issue with checking the timing for the fixation cross or the blank screens. I would like to be able to fix this issue so that I can see the actual time at which the image is no longer being displayed in each trial.

I’m sure that I have left out some relevant details that I am not aware of at the moment, so if I have please let me know and I will fill in the gaps.

Thanks so much!

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Hi Kate,

I don’t know enough about Psychopy to explain why it isn’t reporting the time when your Movie Component stops.

However, there are some previous threads that you might useful. You can try adding some timings to your output yourself using:

thisExp.addData("YourVariableLabel", globalClock.getTime())

If you look at the thread below, there are suggestions for using this with a Code Component. I hope this helps!

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