Millisecond Forums

Setting markers for stimlustimes with Tobii Eyetracker


https://www.millisecond.com/forums/Topic27126.aspx

By Aleya - 5/15/2019

Hi,
I've tried to find a solution by reading previous comments on this topic, but cannot seem to send useful markers for the onset of my stimuli.

It is a simple experiment, in which two pictures (one neutral and one emotional) are shown simultaneously on each side of a fixation cross for only 200ms. Before the onset of the stimuli I want a recorded fixation cross time of 300ms. ITI are fixation crosses as well fr 3000-6000ms.
According to an example script on the millisecond homepage, I tried the following:

<values>
/ trialduration = 2200
/ marker = 0
/ stimulusonset = 0
/ image_neu = ""
/ image_emo = ""
</values>

<port marker>
/ items = (0)
/ port = eyetracker
/ erase = false
</port>

I set up trials for each version emoneu (emotional left and neutral right) and neuemo after defining the pictures and their positions:
<trial emoneu>
/ ontrialbegin = [values.marker = (picture.emoleft.currentindex*100) + picture.neuright.currentindex;]
/ ontrialbegin = [port.marker.setitem(values.marker, 1);]
/ stimulustimes = [0 = fixation; 2001 = emoleft, neuright, marker]
/ posttrialpause = (picture.fixation.item)
/ inputdevice = eyetracker
/ recorddata = true
/ ontrialend = [values.image_emo = (picture.emoleft.currentitem); values.image_neu = picture.neuright.currentitem]
/ ontrialend = [values.iti = trial.iti.timeout]
/ timeout = values.trialduration
</trial>

<list trialselector>
/ items = (trial.emoneu, trial.neuemo)
/ itemprobabilities = (.50, .50)
/ poolsize = 60
/ replace = false
</list>

I cannot seem to get adequate markers for the stimulus onsets. I know I set it up as a multiple digit number to indicate the current index of each picture shown for the left and the right, but they seem to be random.
Also, I would like to also set markers for the fixation cross, so I have a baseline to analyze the data from. I realize that I have to set markers back to 0 if I have more than one in a single trial, but I just want to get the stimulus setting right first.
I'm sorry if this question is trivial, I just don't seem to be understanding how to implement it.
Thanks in advance,
Aleya
By Aleya - 6/10/2019


Thank you so much for all your help Dave! Much appreciated!