FAQ: How can I accurately keep track of reaction times (RTs) for participant responses?

[SR-SUPPORT]

Calculating a reaction time in Experiment Builder requires knowing the times of both the triggering event (e.g. a keypress or mouse click) and the onset event (e.g. stimulus onset). The relevant timing property for trigger nodes is .triggeredData.time, which returns when the triggering event occurred in terms of Display PC time. The relevant timing property of action nodes is .time, which returns when the action was executed in Display PC time.

So to calculate an RT, use an UPDATE ATTRIBUTE action node to update the value of an "RT" variable to the difference between the .triggeredData.time property of the triggering node and the .time property of the onset node. The Stroop example (File menu -> Example) provided with Experiment Builder illustrates the process.

   

Please note that the .startTime property of action nodes returns the time when that node was "entered" - not when it was actually executed, so it should NOT be used for RT calculations.