How do i code? - stroop task with psychtoolbox

Hi all,

Could you please clarify to me how can I code the standard duration of a stimulus (word) if I want the stimulus to diplay at the center of the screen until participant makes a response?

Basically, I have no duration time fixed because it would be the participant response to end the stimulus and began with the other.

StandardDuration= ....?

Many thanks in advance.