InstantForum 2017-1 FinalMillisecond Forumshttps://forums.millisecond.com/Millisecond ForumsFri, 17 Apr 2026 13:01:22 GMT20https://forums.millisecond.com/Topic19065.aspxHi,<br/><br/>I have a couple of questions<br/><br/>1) Is it possible to randomize a trial's duration (either using /trialduration or /response = timeout ())? I want to try and have my intertrial interval randomly vary between 500ms and 400ms on any given trial.<br/><br/>2) I want a particular (mouse-click) response to give participants a 'reward' feedback trial on 80% of trials, while presenting the same mouse-click with a different 'no-reward' feedback trial on the other 20%. I'm not sure how to go about building in these percentages into the branch trials. What's the best way to do this?<br/><br/>Thanks,<br/><br/>JayThu, 12 May 2016 09:38:51 GMT***JayD***https://forums.millisecond.com/Topic19066.aspxRe. #1: Yes. You can do something like<br/><br/>&lt;values&gt;<br/>/ randomiti = 0<br/>...<br/>&lt;/values&gt;<br/><br/>with <br/><br/>&lt;trial iti&gt;<br/>/ ontrialbegin = [values.randomiti = round(rand(400,500))]<br/>...<br/>/ trialduration = values.randomiti<br/>...<br/>&lt;/trial&gt;<br/><br/>/pre- and /posttrialpause, /timeout and /trialduration all accept values which you can set at will via /ontrialbegin etc.<br/><br/>For the relationship between the various timing components involved in a &lt;trial&gt; see the "<span class="header1">How to Control Trial Duration and Inter-Trial Intervals" topic in the documentation.<br/><br/>Re. #2: Not sure why you would need any elaborate /branch logic, but the question is underspecified. For example, it's not clear if the "specific response" is the only allowed response; if not, you cannot possibly know how many times a participant will actually provide the "specific response", i.e., it may not even be possible to achieve the 80/20 split. Suppose the participant only provides the "specific" response twice across however many trials you have: You could at best achieve a 50/50 split in that situation.<br/><br/>If, otoh, there is only that single "specific response", you can simply do<br/><br/>&lt;block someblock&gt;<br/>/ trials = [1-10 = noreplace(rewardtrial, rewardtrial, rewardtrial, rewardtrial, norewardtrial)]<br/>...<br/>&lt;/block&gt;<br/><br/>which will run 8 "reward" trials and 2 "no reward" trials. No branching required.<br/><br/><br/></span>Thu, 12 May 2016 09:38:51 GMTDave