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'sync rt with screen' from builder does not work

Hi,
I’m building an experiment using the builder, and in the experiment there is a bouncing ball and the subject needs to press space when the ball hits the ground.

I want to get the precise times when the use hit ‘space’.
currently not matter whether I choose the ‘sync rt with screen’ option in the keyboard component or not, the RT’s that I get for the keyboard responses are always synced with the screen.

I’m checking whether they are synced or not by diffing sequential reactions, and that difference is always a mutliple of 16 ms (the length of a frame).

the code that checks whether or not the RT’s are synced:
diff = [data[i] - data[i-1] for i in range(2,len(data))] diff = [1000*a for a in data] print(diff)

I would appreciate if someone could tell me what am I doing wrong and how I can get the actual time when the subject presses the ‘space’ key.

thanks.