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duration of stimuli synced - Printable Version

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duration of stimuli synced - bisserai - 09-28-2021

Hi FF team,

It's me again and with the same study, but facing another problem. I would like to present a fixation cross which stays on while an audio stimulus plays and once the audio finishes i'd like to have the fixation cross disappear and the response buttons appear. Everything is working except i can't get the end of the audio to trigger the fixation cross to leave the screen. I've tried using the group function, where my audios are defined like so:
  "type": "audio",
  "content": "V1L.wav",
  "visible": false,
  "delay": 1.5,
  "barrier": true,
  "group": "group1"

and my fixation cross defined like so:
  "type": "text",
  "content": "+",
  "size": "150px",
  "alignment": "center",
  "duration": "%sgroup:group1"

The trial template is defined like so:
"audioP": {
    "type": "basic",
    "stimuli": [["fixx","V1L"], ["fixx","J1R"], ["fixx","M1R"]],
    "responses" : ["v1","j1", "m1"],
    "submission_point": false,
    "stimulus_pattern": {"order": "random", "attribute": null, "pre_shuffle": false}

From a previous study where we used the group function i remember the audio had to have barrier set to false, so i also tried that, but it didn't have the desired effect so i put it back to true, since i need that to delay the appearance of my response buttons. I played around with the duration characteristic, but i didn't seem to get anything useful out of it...

Your advice will be much appreciated!


RE: duration of stimuli synced - Ting - 09-29-2021

Hi Bissera! Always happy to help!

For however much I can remember, the relative duration feature was specifically for audio responses, because you needed the background audio response to record a variable length that depends on the audio stimulus. The current case sounds like a different setup, where you want the fixation (i.e., a text stimulus) to disappear after a variable duration?

If so, a solution available right now would be using the "trial yoking" method. Essentially, you'd put the fixation and the audio stimulus on one trial template, the response on another, and yoke the two trial templates together. We have a tutorial on this in case you haven't come across with it yet:

That way, the fixation "disappears" automatically because the experiment moves onto the response trial after the stimulus presentation. You won't need to specify the duration of the fixation anymore as it just concludes with the end of the trial. Let us know if this works!

RE: duration of stimuli synced - bisserai - 10-04-2021

Thanks so much! I didn't realise i could yoke stimuli and responses between trial templates and this was why i had them both on a single trial template.. many thanks for sending the tutorial, the experiment works as intended (: