libet clock

Hi all,

I’m trying to set up an experiment that involves a movie clip being played continuously. While the movie is playing, the participant presses a key on the keyboard. Upon keypress, a tone is provided as feedback. I would like the tone delivered NOT instantaneously, but at some time delay.

One of the variable is the probability that the key press can produce the tone (which is 0%, 50%, 75% and 100%). How can i make that happen? should I make 2 trials with 0 and 100% chance of producing the sound, and then tweak it to obtain the 50% and 75% codnition, or is there a way to round it up into one event for each probability?

Best regards,


For your first question, I suggest using the Trial Variable feature for type “Reaction Time”. If you go to the Experiment menu you will see Trial Variables in the menu.

Regarding your second question, can you explain in more detail about how using the tone and percentage probabilities work together?

for the first question, i’e managed to introduce the said delay with a sound editor. for the second question, i’ve made another topic describing the issue with a reater precision( ). thanks a lot