Lack of acc in calculating reaction time in OpenSesame

Gio38000 · May 2022

Hello, guys!

I hope you're doing amazing.

Today I have a problem with the reaction time calculation. I have read in several comments that it is enough just doing a subtraction between "t2" which is often the kb.get_key() and "t1" which is often "canvas_1.show()". Meaning the time when the key is registered minus the time when the 1st stimulus appears. However, doing this calculation over and over again, I obtain just the duration of my two canvases regardless of the real reaction time.

As you can see in this screenshot, I have: (a) one canvas lasting 695ms, (b) a second canvas (which is just a white mask) lasting 239, and (c) my kb_response with a timeout = 100. With this, participants should have 1,034ms available to respond. The thing is that when I do the subtraction t2 - t1, I always obtain around 934ms meaning the duration of my two canvases. Normally I should obtain between 400ms and 600ms.

I have already tried to give 339ms to my second canvas and 0ms to my kb_response timeout, but it is always the same.

In the 1st screenshot, you can see the code and in the second one, you can see the subtraction.

Another thing is that pressing the key should not make the next stimulus appear. It means that all the canvases should last what I want regardless of the participant's reaction time. But, I have the impression that pressing the key shortens the displaying time of my canvases.