Track location of mouseclick and correct randomization

Luukvk

Hello,

I am trying to create an experiment in which participants have to click on certain pictures. Keep in mind, I am very new to Open Sesame.
Basically, the participants will see a screen with a certain number of pictures of two dimensional shapes. The screen will then go black. After that, they will see the same screen as before, however there is a fifty percent chance that one of the shapes has been changed. The participants would then have to click on the shape that they think has changed, or on some other button if they think no shape has changed.

There are two main difficulties at this point. First of all, it seems like there is no option in Open Sesame to check if the participant has clicked on the right picture. It seems like Open Sesame can only track if the participant has clicked, not where or on which picture. Is this true?

Furthermore, I'm having trouble finding a way to implement that there is a fifty percent chance of one random shape changing. I guess I could put a condition in the block loop like 'shape_changes' with the options yes and no, and then do full factorial design. However, how could I then implement that one of the pictures (randomly chosen) would then change into another random picture?

sebastiaan

There are two main difficulties at this point. First of all, it seems like there is no option in Open Sesame to check if the participant has clicked on the right picture. It seems like Open Sesame can only track if the participant has clicked, not where or on which picture. Is this true?

No, it is not . You have a few options:

• The mouse_response item will create the variables cursor_x and cursor_y, which you can use to determine on which picture participants clicked.
• The touch_response item allows you to divide the display into a grid, which is any easy way to find out where (approximately) participants clicked.
• The image_button widget of a form allows you to implement clickable images.

Furthermore, I'm having trouble finding a way to implement that there is a fifty percent chance of one random shape changing. I guess I could put a condition in the block loop like 'shape_changes' with the options yes and no, and then do full factorial design. However, how could I then implement that one of the pictures (randomly chosen) would then change into another random picture?

Do you mean that you want to have a random association between a picture variable, which would be one column in the loop, and a variable shape_change, which would be another column in the same loop?

If so, then you could use the shuffle operation of the loop, which allows you to shuffle one column independently, thus causing a random pairing between that column and the rest of the columns.

• http://osdoc.cogsci.nl/3.1/manual/structure/loop

Cheers!
Sebastiaan