Forced Choice Image Presentation (case 14147)

[Rachael]

Hi,

Was wondering if anyone could help with how to program a forced choice image presentation. Ie. I want to have two images presented side by side (if possible with a text question also on screen), which the participants would respond to/indicate their decision via the keyboard?

One of the images would be from earlier in that trial, and the other randomly selected from the same stimlist.

Would there also be a way to randomise which side of the screen they were presented on?

Thanks!

[jason_reed]

Rachael,


To find insructions on how to put two images on the screen at the same time as well as an example input file, please refer to the Compound Screen section of the DirectRT manual: http://www.empirisoft.com/directrt/help/directrt_samples_compound_screens.htm.


To randomly detemine whether an image will appear on the right side or the left side, the most straightforward way is to create two different conditions-one in which image 1 appears on the left and image 2 appears on the right and one in which image 2 appears on the left and image 1 appears on the right. Take a look at the attached files to get an idea about how to do this.


Finally, take a look at the stimlists section of the DirectRT manual for specific information about randomly selecting stimuli for presentation: http://www.empirisoft.com/directrt/help/directrt_stim.htm


Please let me know if you have any questions.


Jason

[jason_reed]

Here are the rest of the files that you would need.

[Rachael]

Thanks, Jason! That was helpful.

I've created an input file using those instructions, and now I'm just trying to work out whether everything is presenting okay. However, for some reason when I try to run the file, it comes up with a message saying 'Row 2 has a missing value for one of it's time columns'. Can't seem to find a gap in the spreadsheet, though?

I've re-written that row, re-saved it as a CSV file, double checked that the regional settings save everything as comma delimited etc, and still having this issue. Not having an issue running other input files...

[jason_reed]

Rachael,


Thanks for uploading your input file. It was missing the bgr column and did not have the bgr, wgr, and style columns in the same order as the default input file in the DirectRT folder on your computer. I also eliminated any column headings from the first row that did not have a corresponding entry in the second row; this is more of a preference thing.


Try using the attached file and let me know if it works.