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Auditory Inter-stimuli interval discrimination task

Hi everyone!

I need your help and expertise! I am a new user of opensesame and I am trying to create an Auditory Inter-stimuli interval (ISI) discrimination task. In the task the same beep is presented in a sequence separated by two different ISI: short (1350) and long (2000). The short ISI (75%) is more frequent than the long ISI (25%).The subjects are supposed to press a key (space) when they detect a long ISI in the sequence. The main objective is that the sequence play without interruption and that the subjects can response each time the long ISI appeared. I will like to register the responses and the absence of responses.

I had been trying create the factorial design of variables but I failed, as i don´t know how to defined levels.

I had been trying 3 ways to achieved my objective:

1.using a sound file that already have the sequence on it and collect multiple keyboard responses (with one line per keyboard response in the csv. file); while playing the file. I found this in this forum: But I can´t make this works.

2.using the sound followed by an advanced delay that will be program as ISI. In this case I don´t know how to register answers that are going to take place during the delay.

3.using just the samplers and adding the duration of the ISI plus the duration of the beep. Sound_A: 1400 ms duration (1350 ms de ISI and 50 ms the beep). Sound_B: 2050 ms duration (2000 ms ISI and 50ms beep). With this files i create a sequence. This options runs correctly but I don´t know how to collect the answers.

I am just interested in one sequence or set (not all combinations). If you can help me I will be really greatful.




  • Hi SOL,

    These kind of problems, I usually approach using while loops.

    Generally, the procedure is to implement a sequence that is repeatedly executed while a certain action can occur at any moment. So, in your case, you start the loop, and in the beginning you wait briefly for a keypress (few milliseconds only), if a press was detected, process it, otherwise continue with the procedure. Here you add everything that should happen in the mean time, while you are waiting for the keypress, or some other stopping criterion is met (e.g. certain number of repetitions).

    That has of course the disadvantage that you have to code it yourself, and can't really enjoy all of Opensesame's items. But the gain in flexibility is totally worth it!

    Does that make sense?


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