Exogenous cueing task

LauraSa · May 2019

Hi,

I have a randomization problem in OpenSesame.

I have to create a dot detection task driven by an exogenous spatial cue. Each trial will begin with a fixation cross (+) flanked by two blank squares on its right and left side. Then a cue (a face displaying one of 5 different emotions) will appear in one of the two squares in randomized order, followed by a dot presented in one of the two squares, in the same (valid trial; 70% of total) or in the opposite (invalid trial; 30% of the total) position as the cue (in randomized order).

I have 10 different faces for each facial expression.

So I have to randomize both the facial expressions and the trial validity considering that for each expression I should have 70% of valid trial and 30% of invalid trial.

I am not familiar with opensesame (I have used Matlab in the last studies) and I don't know how to do that.

Any help would be greatly appreciated!

Laura

eduard · May 2019

Hi Laura,

First of all, I recommend you doing the beginner's tutorial: https://osdoc.cogsci.nl/3.2/tutorials/beginner/

This will already help to make clear how Opensesame works in general.

For your specific example, I am not sure whether you can achieve what you want to, using only the loop table and standard items. I would use inline_scripts instead.

If I understood correctly, you have 3 variables.

Emotion (5 levels) x target side (2) x cue validity (2), right?

So to make it completely counterbalanced (and have the same likelihood of invalid and valid trials at each location), you would need 100 trials.

import random
emotions = ['emo1','emo2','emo3','emo4','emo5']
cue_pos = ['left', 'right']
cue_valid = [0,0,0,1,1,1,1,1,1,1] # 0 represents invalid, 1 is valid

trials = []

for em in emotions:
   for pos in cue_pos:
      for va in cue_valid:
         trials.append([em,pos,va])

# shuffle everything so that you have it randomized
random.shuffle(trials)

# next you have to assign the target position based on the cue position
# and the cue validity
# also you need to select a random emotion from the emotion category, e.g.
# using random.choice()

This should get you started. Let us know if you need help.

Eduard

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