change detection task
I am trying to program my first experiment, which is a change detection task. The participants are presented with 2 or 4 face pictures and after a short break are again presented with 2 or 4 pictures, one of which could have changed (new face). The task is to indicate whether a change has occurred or not. Before the initial picture presentation arrows indicate on which side, left or right, a change could occur. I have an item pool of 24 pictures which should be paired or grouped randomly, without showing the exact same coupling twice. If a change occurs the new face should have the same sex as the face in the picture before, otherwise sex does't matter. I'd like to have a total of 768 trials, with 50% change trials, half of which with 2 and 4 pictures, equally distributed on the top and bottom half of the screen and on the left and right side (indicated by the arrow cue).
So the sequence would look like this:
arrow cue: left or right
memory array: 2 (both at the top or both at the bottom of the screen) or 4 pictures, randomly drawn from a set of 24
testarray: 2 or 4 pictures, same as in the memory array except in change trials: one pictures changes (only in direction of arrow cue)
I'm having problems with selecting random pictures from the item pool and making sure that the change picture (in the testarray) has the same sex as the picture in the memory array, cause I'm also not sure on where to define this.
My second (big) problem is that I don't know how to vary between the presentation of two or four pictures; I tried to implement multiple sketchpads with two or four placeholders for the pictures and a variable show,,if comment but then I don't know how to insert the pictures into that. I guess I should use an inline_script, but as I am rather new to this, I really don't know on how to start. If anyone could make any sense out of any of this, I would be really happy and would appreciate the help.