Divide reaction time in a phase where no reactions /where reactions are registered?

[clueso]

Hello!
I would like to conduct an experiment where probands have to watch some video clips (1000ms) and react during or after the single videos (limited RT (again 1000 ms) via Min-Max (0-2000!)). If the person reacts or the video clip ends – the next stimuli will start (using ! in style folder-options). In this case it could happen that a person reacts to slow (>2000 ms), while the next video clip has already been started, so that the reaction is directed to the next video (although the proband wanted to react to the previous video). Is there any possibility to create a kind of time limit (in my case 500 ms) where any reaction of the proband will not be recorded AND will not have an influence on the continuous progression of the further video clips?

[jarvis24]

I think I understand, but if they miss the first video and respond late (e.g., during the second video clip) then that would be registered as a response to that subsequent video. So how would you then get a response to the subsequent video? You know what I mean? I can think of a couple possible workaround for this but it would depend on 1. how many videos you have in a trial and 2. whether a single or multiple valid responses are available.

[clueso]

Dear jarvis24,

that’s the main problem. Sorry for my inexact description. I don’t get a reaction to the subsequent video: of course technically the reaction is related to the subsequent video because it has already been started when the participant reacted but e. g. if the reaction was about 100 ms and there was no reaction during the previous video – I can assume that the person just reacted too slowly and that this reaction was actually directed to the previous video. In this case I registered no reaction during the first video (which I can interpret that the participant was not able to react during the limited reaction time for this video) and a very quick – too quick reaction during the second video clip. In this scenario the participants misses the “real chance” to react to the second video because at this reaction time it’s impossible to perceive the video and show the questioned reaction.


In this regard it would be perfect to implement a kind of time limit during every video where any reaction has no impact on the full presentation of the video followed by a phase where it is possible to react (in this case during the last 500 ms of the presented video + 1000 ms RT whereas no reaction should be registered during the first 500 ms of a video clip).


1. how many videos you have in a trial: altogether 130 videos (3 blocks with 50 videos– short break – 50 videos – short break – 30 – videos)
2. whether a single or multiple valid responses are available: single response.


thanks

[jarvis24]

OK, I think I'm almost with you here. Let's use a concrete example.

Our proband sees video1 for 1000ms, there is 1000ms delay (blank screen) and then video2 appears for 1000ms again followed by 1000ms of delay (blank screen). Suppose our proband ought to press the space bar to react when they see a type of target in any of the videos. Both videos are displayed within a single trial. Is this a kind of scenario this issue could apply to? E.g., the proband sees the target in video1 but responds 2300ms after onset of video1. And SO, it appears that no response to video1 occurred and that the response to video2 was 300ms. Am I in the parking lot of the ballpark here?

And if I am then we need a way to identify this occurrence in the data--yes?

____

PS., I have to admit I thought proband (above) was a typo but I checked first and have been educated! From Wikipedia:

Proband, or propositus, is a term used most often in medical genetics and other medical fields to denote a particular subject (person or animal) being studied or reported on...

for curious users, see more at http://en.wikipedia.org/wiki/Proband

[clueso]

Exactly, that’s an adequate scenario. Therefore the proband (smile) "lost“ the chance to react to the second video actually because his reaction was mentally addressed to the first video. In this case he showed an incorrect reaction twice: There was no reaction for the first video and a wrong reaction (for the most part) to the second because in my experiment at least 600-700 ms of a video clip have to be watched to be able to show the right reaction.
Thanks.