I am doing a matching to sample task, where two pictures appear above center as the "samples" and one picture appears below as a "target". Participant decides if the target matches either of the samples. I have 56 different pictures in events. Each picture repeats 4 times, but in different locations that I have already designated by pixels to the horizontal and vertical of center to be left and right visual field (lvf and rvf, respectively): For example, I have picture1 lvfsample, picture1 rvfsample, picture1 lvftarget, and picture1 rvftarget. This makes 224 events plus a Center X event. No help needed on that. Here's my difficulty: on a trial I want the center X to appear and remain for the duration of the trial (that is until the participant makes a response). After 3000 ms of X, I want the X to remain and three of the events (e.g., lvfsample, rvfsample, and lvf target) to flash simultaneously for a duration of just 200ms, after which just the central X remains, awaiting response from participant if they didn't respond during the 200ms picture presentations. The response is a simple key stroke (any key accepted). Once the participant responds, the next trial begins with the central X and so on. There will be about 800 trials in all (divided into blocks, no problem). I have already determined which three pictures appear per trial, so I need no help there.
Currently, I can make all three pictures plus the X appear in a flash simultaneously. The problem is that I can't make the X act independently of the three pictures. I'd also like the RT recording to begin at the onset of the three pictures, not the onset of the central X at the beginning of the trial. That way, participants can respond during their presentation or after their offset when it's just the central X. If that RT recording can't be set to coincide with picture onset, it's ok, as I'll just subtract 3000ms from the trial RTs to get an accurate number. So, the whole trial should last 3000ms+200ms+any additional RT. The big issues are:keeping the X on the whole trial, flashing pictures for 200ms after 3000ms of trial onset, keeping the trial on with the central X until participant makes a response.
Currently, I can make all three pictures plus the X appear in a flash simultaneously. The problem is that I can't make the X act independently of the three pictures. I'd also like the RT recording to begin at the onset of the three pictures, not the onset of the central X at the beginning of the trial. That way, participants can respond during their presentation or after their offset when it's just the central X. If that RT recording can't be set to coincide with picture onset, it's ok, as I'll just subtract 3000ms from the trial RTs to get an accurate number. So, the whole trial should last 3000ms+200ms+any additional RT. The big issues are:keeping the X on the whole trial, flashing pictures for 200ms after 3000ms of trial onset, keeping the trial on with the central X until participant makes a response.

Comment