Yoking Stimuli, Selecting Distractors, and Using Home Key

Hello,
I'm trying to create a match-to-sample task. I need to be able to present a random stimulus from a list in the "probe" location and simultaneously present that same stimulus (or one from the same position on a different list) in the "target" location. In reading about yoking, it appears as though that only works across trials rather than within trials. Am I incorrect?
For clarity, I also need to simultaneously present 5 distractors from the same list as the probe, but none can match the probe.
Finally, I would like to use a home key. That is, a key press to start the trial, a key release to clear the screen and measure decision time, and RT to continue recording until the answer key is selected. Is this possible?
Many thanks,
Meredith

Hi Meredith,

The best place to start when completing an experiment like this would be the 'yoking random pairs' sample within the advanced (part 6) section of the sample library included with DirectRT. As long as your copy of DirectRT is version 2006 or newer, this experiment shouldn't be too much work to properly create.

This should definitely work within trials - as the samples completes itself in this method.

To read up more on stimulus lists, see the following link: [url]http://www.empirisoft.com/directrt/help/directrt_stim.htm[/url] (scroll down to the StimLists section)
To see more on the yoking sample, see this link: [url]http://www.empirisoft.com/directrt/help/directrt_samples_v2006_yoking.htm[/url]

Please let me know if you have any additional questions or if I can help in any way.

Regards,
Trevor

Hi Trevor,
Thanks for the information on yoking, but I still have a question about using a home key. Ideally, subjects would have to press and hold on the spacebar to make the stimuli appear, then release the spacebar to indicate their responses. When they release the spacebar, I would like for the screen to clear to ensure they've made their decision before letting go of the home key, and I would like the key release time to be recorded (as well as total RT for the trial).
Finally, if I'm yoking random pairs, is there a way to make sure that other stimuli in the same trial (the distractors) aren't identical to the yoked pair (that is a combination of random sampling without repacement and yoking within a trial)?
Best regards,
Meredith