An experiment consisting of two different tasks

EllaGivon

Hi there

I have designed an experiment that consists to tasks that should run alternately (specifically, each trial consisting of an emotional task followed by a faces task).

In each block, there are 40 unique stimuli for each task (40 emotional images and 40 photos of faces). I want the block to randomize both tasks but I don't want the block to run the same stimuli (emotional or face) twice.

My problem is as follows:
If i create one loop for both tasks, then a specific emotional stimulus is always followed by a specific face stimulus, such that the emotional task is randomized but the faces task is not.
If I create 2 loops and for the second one define 0.03 cycles then it goes out of the loop and potentially repeats stimuli that were already presented.

I know that for now there is no "nested list" like in E-prime, but any suggestions for a way to solve this?

TNX,
Ella

eduard

Hi Ella,

Since the latest release of Opensesame, the loop table has quite a few advanced randomization techniques. Perhaps one of them will suit you well, however, I have never bothered reading them in detail (shame on me), but instead I can suggest you something else.

One loop will suffice. But instead of defining your face and emotion images in the loop table, you do it beforehand. In an inline_script, right before the loop, you make a list each, and randomize it. In the loop itself, you can add a variable coding the trial number. Inside the loop, you need to index the stimuli_list with the current trial number, in order to get the current image. Everything else will be the same.

import random
var.emotion = ['anger1.jpg','anger2.jpg','anger3.jpg','anger4.jpg']
var.face = ['face1.jpg','face2.jpg','face3.jpg','face4.jpg']
random.shuffle(var.emotion)
random.shuffle(var.face)

Let me know if you need more help.

Edaurd