We are using Superlab 4.5 to program a reaction time task (Serial Reaction Time Task). Basically, the task consists in displaying a circular cue at one of four positions on the screen and recording the response of the participant with a response pad (not the Lumina fMRI response pads fro Cedrus). Once the participant presses the correct button, we have a 400ms interstimulus interval and then present the next circular cue at a new position, and so on for 900 stimuli (in about 15min).
We are now integrating this task in an fMRI setting and would like to have an event-related design, with the finger presses as events. This requires synchronizing the recorded finger presses with the fMRI acquisition. We synchronize the beginning of the experiment with the trigger sent by the scanner, but cannot synchronize the beginning of the following trials in the same way, as they depend on the reaction times of the participants.
When I first measured the total duration of the experiment with a stopwatch, it was about 10s longer than by adding up all recorded reaction times and interstimulus intervals. Then – by going through the numerous threads on timing in this forum – I discovered that there was a checkbox to record the cumulative time in a column of the .txt file. When I compare the final cumulative time with the time measured by the stopwatch, they seem to match! Like that, the errors don’t add up along the experiment.
However, I would like to check how much off individual reaction times and interstimulus intervals can be. For that, launching Superlab in verbose mode seems promising, but I don’t know how to do that. I read the posts by Hank on the subject and tried to download his little script, but don’t know how to execute it.
We are using a MacBook Pro (2.66 GHz Intel Core I7) with Mac OS X 10.6.8.
Thank you in advance for any help, comments or suggestions!