Jittering fixation durations

[ssyoon]

Hi,

I'm wondering if there is a way to jitter fixation durations randomly.
For example, instead of using a specific fixed duration for 'trial_duration' (e.g., 2000 ms), I'm wondering if I can change the duration so that 'trial_duration' can be between 2-4 seconds that vary randomly trial-by-trial.
If you could share any ideas about this, it would be appreciated.
Thank you for your help in advance.

Best,
Sangsuk

[becky-gilbert]

Yes, you can do this using a function for the fixation's duration parameter. There's one example here: https://www.jspsych.org/tutorials/rt-task/#part-7-using-functions-to-generate-parameters

And here's another example for writing a function that will randomize between 2 and 4 seconds:

var fixation = {
  ...
  trial_duration: function() {
    var rand_iti = Math.floor(Math.random() * (4000 - 2000)) + 2000;
    return rand_iti;
}

[ssyoon]

Thank you so much for your answer!
This works perfectly!