Dual-task paradigm with visual and auditory probes, spoken and key-press responses

I'm starting to set up a new experiment that is rather complicated, so I thought maybe I could get a few quick tips here to minimize the amount of time I was on sub-optimal or inefficient task set-up.

The experiment involves the presentation of both visual and auditory probes, and the collection of spoken responses (to the visual probes) and key-press responses (to the auditory probes).


Here’s the basic set-up:

Task 1: A social category label will appear on screen, and participants will generate responses aloud. At the same time, the computer will emit tones at a prespecified frequency (e.g., once every 750 msec), and participants will respond by pressing a key on the keyboard as quickly as possible in response to each tone. I need the label to stay on the screen for the 2-minute duration of the task, and I need to record (1) the onset time for each spoken response and (2) the response and RT to each probe.

Task 2: A visual array of numbers will appear on the screen; these numbers will appear in black/white font and at random intervals one of the numbers will change (e.g., become red) and participants will respond by speaking the number aloud. At the same time, the computer will emit tones at a prespecified frequency (e.g., once every 750 msec), and participants will respond by pressing a key on the keyboard as quickly as possible in response to each tone. I need to record (1) the onset time for each spoken response in relation to the changing visual array and (2) the response and RT to each auditory probe.

If anyone has experience with this kind of thing and can anticipate the kinds of errors I'm likely to make in setting this up or has tips/tricks that are helpful, I would really appreciate it!

FYI, MediaLab actually has a function setup to do stuff like this. If you have access to it, you might be up and running faster. Check this out and see if it helps:

[URL]http://www.empirisoft.com/Support/showthread.php?t=375[/URL]

Try also doing a general search on "probe" here on the support site and you might find some other useful links.

Hi Blair,

The ML/DRT combo you suggested was useful, but now I have a new task and again find myself stumped. I did a search for "probe," but haven't found anything that addresses my problem.

Basically, I need to run the primary task through DRT, not ML, because each trial has multiple events that need to be time-controlled. More specifically, I have a sequence of 5 image stimuli with a total presentation time of 5 seconds. I want to add an auditory probe that has a duration of 500 msec and is presented at intervals of 750-1250 msec, to which participants will respond by speaking into a microphone. (Participants will not respond to the images.)

So, I need to present multiple image files and have auditory probes coming up at variable intervals, and I need to record auditory responses to each of these probes. Is this possible?

What I would probably do in that case is create multiple sound files with variable delays before the tone occurs. Randomly select one of those sound files on each trial *before* the images appear and specify a [I]0ms[/I] time value so there is no delay between the onset of the sound file and the onset of the images. Then use "[I]RT:any[/I]" (or whatever) for each image and apply a [I]min-max[/I] value of [I]0-1000![/I] for the trial's style. That way, each image will only be on the screen for 1000ms, but will record the RT to the sound file if it occurs during its interval. I just made that up--does it make sense?