Randomize 2 variables with several levels

Naïde

Hello,

I am currently programming an experiment in which I want to present a list of 36 words. In this list, 12 words are positive, 12 negative and 12 neutral. I have another variable which is the value of the word (high vs low), which means that I want each word to be randomly paired with a number between 1 to 5 (low) or 8 to 12 (high). Additionnaly I need to counterbalance the proportion of high vs low value word between each emotionnal condition (half of positive words with high value and the other half with low value).

Is there any simple way of doing so ?

With E-Prime I used the nested lists functionnality, but I can't fin a way to easily programm my experiment with Open sesame.

Any idea would help :)

sebastiaan

Hi @Naïde ,

Since you have only ten numbers (and twelve words per emotion), I assume that you want to randomly sample from these numbers with replacement. If so, then it's actually quite easy, because you can simply create a loop table with three columns: word , emotion ('positive', 'negative', or 'neutral'), and value ('high' or 'low'). Then at the start of the trial sequence, you insert an inline_script with a short piece of code in the prepare phase to actually set the number variable, like so:

import random
if value == 'low':
    number = random.randint(1, 5)
else:
    number = random.randint(8, 12)

Does that make sense?

— Sebastiaan

Naïde

Hi @sebastiaan

Thank you very much for your help. The code works perfectly to randomly assign a number. The problem is that I also want to randomize the high / low value for the words. For instance I want the first positive word to be either low or high value across participants.

I tried to creat one loop table with 3 columns corresponding to the 3 emotional conditions (positive / negative / neutral), and then a sub loop table with a full factorial design leading to 6 conditions (positive-high, positive-low, neutral-high, neutral-low, negative-high, negative-low).

Before these loops I placed the following inline_script to define the value (high/low) and randomize the numbers

import random

low=random.randint(0,5)

high=random.randint(8,12)

Now I would like to

1/ randomly assign a value high or low to each word

2/ counterbalance the proportion of high / low value words within each emotional condition (e.g. 50% of positive word with high value and 50% with low value)

I tried to import pseudorandom tu use the constrain function but it doesn't work. Opensesame indicates that pseudorandom is imported but not used.

I am sorry for these basic questions, I am a new user of opensesame and not familiar with Python (it took me a while to figure out how I could import the random plugin...)

Again, thanks a lot for your answer and your help :)

eduard

Hi,

See attached experiment for a demo how you can accomplish this with Python coding.

Newexperiment.osexp

Essentially I create the stimuli once per block, and then access them one by one in the trials. When doing that that I get 36 words, 12 in each valence condition and of these 12, 6 with a high number and 6 with a low one. That's what you want, right?

Eduard

Naïde

Hi @eduard

Your programm is wonderful, the randomization is perfect !!

Thank you so much for your help ! 😀

The only issue I have now is that among the 12 words of each valence condition, some are presented several times while some do not appear. Is there a way to tell the programm that once a word has been presented it must not be presented again in the following block ?

Experience_V4.osexp

Naïde

@eduard

Finally it works perfectly for me, you saved me a lot of precious time !

Thanks again !