In the study we are presenting participants with spoken sentences they have to passively listen to and at some points, they have a task that serves as a means of attentional check. After a number of sounds (always different), a written sentence is displayed and participants have to indicate whether the written sentence matches in meaning with the previous sentence they heard (see the screenshots below for the flow of both, spoken and written sentences respectively). For that, they have to press either ‘F’ (‘yes’) or ‘J’ (‘no’). The spoken sentences are .wav files and every written sentence is a .jpg file. In every loop, images or sounds, respectively, are being pulled from a spreadsheet. (Note that images and sounds are in separate .xlsx files and I have manually set when the written sentences appear because I was not able to find a better and easy solution to randomize the presentation of the images after a random number of sounds and set the button press for image trials only.)
The flow of the experiment goes as follows: a set of instructions are first presented and then a short Training (TR) block starts. Every trial containing spoken sentences has a first interstimulus event of 500 ms because I read that it prevents from cutting the sound files since they are very long and some of them are actually cut.
After that, 3 testing blocks follow (Block 1, 2 and 3). The I/O component is set at the beginning of every sound trial; time set at 500ms + the onset of the interesting point in the sentence. The number of the specific trigger is also pulled from the spreadsheet that contains the list of sound files, from the column ‘portNumber’.
Since the parallel port is not an official cable but bought in Amazon, the bites are sent reversed, so that trigger 1 is 64 in the acquisition screen, 2 is 32, 3 is 96, 4 is 16, etc.
The parallel port is registered under ‘Preferences’ tab as shown here:
in which the address is taken (0x3FB8).
Moreover, two files are included to help send the triggers correctly to the parallel port (‘inpout32.dll’ and ‘inpoutx64.dll’):
The main problem is that when I run an empty EEG as a tryout to check the triggers, in some of the trials are not being sent, last time it was in 3 out of 5 trials of Block 2, and 2 out of 6 in Block 3. I want to make sure the triggers are always being sent when expected.
I hope this was a clear explanation of the experiment and about the problems that I have been encountering. I appreciate very much your time and help.