Logger item does not record response time and causes a delay where it is placed

CSho1 · January 2020

Hi everyone,

I am new to this so sorry if I am missing something obvious. I have spent days looking through previous posts but I can't find a solution to my problem. I am creating an experiment where each trial is: an image for 1000ms, followed by a target (picture of an arrow) for 150ms, then the previous image is repeated for a further 400ms, then the sequence is finished with an inter-trial interval randomised between 1000-1500ms. Participants will be asked to press either 1 or 2 depending on whether the arrow was facing left or right and will respond once they see the arrow. For each trial, I need to log the file name of the image shown, the file name of the arrow shown, the response (1 or 2) or whether the response was correct as determined by the correct_response variable, and the response time.

I have added a logger item but it does not record the response or response time, and it causes the stimuli around it to show for longer than it is asked. E.g. where it is at the moment (at the end of the sequenc) is causing the inter trial screen to present for several seconds.

Please could somebody advise me on where I am going wrong?

I also need to add triggers to be sent to an EEG recording at target onset and response. I would appreciate any advice on this too but I need to get the basic sequence and logger working too before I add the triggers.

Daniel · February 2020

Hi,

Just to be sure, wouldn't you want to place the keyboard_response item after the target sketchpad? I assume you want to collect responses to the target when it is shown and not before that.

Regarding the logger item: it does take a few ms to write the logged data to the disk, but nothing substantial. I don't see anything wrong with your experiment's structure (except for the thing mentioned above), so I don't know why it is showing such peculiar behavior. Have you tried running the experiment on a different computer to see if the problem also shows there?

@sebastiaan do you have a clue what might make the logger sluggish? I think the longer times may also be the preparation time for the next trial and have nothing to do with the logger. This is a known issue with expyriment, so switching from expyriment to another backend may make things run smoother. Can you try this?

Regarding EEG signals, please check https://neuroinformatics.gr/node/37 and https://osdoc.cogsci.nl/3.2/manual/devices/parallel/