Keeping image on-screen for a fixed window

[jarvis24]

[edited from support email]

Is it possible to collect response data and maintain stimuli on the screen for a predetermined length of time? I am displaying pictures for either 1 or 3 seconds (and it is necessary that the pictures actually be viewed for that set amount of time), but I would like to obtain a response (yes/no) and a reaction time while the images are being displayed. It's critical that the pictures to be viewed for exactly 1 second or exactly 3 seconds. Is this possible?

[jarvis24]

See the section in the guide on "min-max" settings, specifically the use of the "full" keyword. e.g., if you have a min-max RT setting of 0-3000 for a given trial, you could simply request your RT like this:

 
RT:53,44,full

Where full asks DirectRT to keep the stimulus onscreen for the full max value regardless of when the RT occurs.

[jcallaire]

I am having a similar problem, and I think my problem stems from not knowing where to put the min-max durration.

I am doing an N-back task and I want a letter to stay on the screen for 2 seconds and if no response is made I want to go to the next letter. Of course if a response is made I want to move on.

I tried all permutations of adding min/max duration, clear-1, -1 (see below) and I can’t get it to work perfectly.

0-5000! rt:1,2-1,full,clear-1

i attached the first 2 lines of my program below. Any guidance would be much appreciated.

jason

[jcallaire]

nevermind i figured it out =p

[jarvis24]

May I ask what you figured out? Just in case anyone has a similar problem?

[jcallaire]

Well the problem is the manual doesn’t tell you were to put the min-max info (at least where I was looking), and if it does then I apologize.

So I figured it out by looking at other programs.

(1) in the styles file I put 0-2000! in the min-max column (that’s where it goes!)

(2) then in the “time” column of my program I have:

rt:1,2,-1,clear-1

This results in showing my stimulus for a max of 2 seconds. If the participant doesn’t respond then the non-response is recorded (-1) and the next stimulus is shown. If the participant responds with in the 2 second window the next stimulus is shown (clear -1).

Now all I need are my button boxes (cough) and I can run this bad boy all day!



jason