Stimuli presentation ratio

We are trying to produce a Go-No-Go task where “go” stimuli are presented 80% of the time on go-predominant blocks, and “no-go” stimuli are presented 80% of the time on no-go-predominant block.

We have tried setting condition expression for the block to 80% for stimulus lists coded as “go” - this didn’t work. As soon as the precentage of trials hit 80%, the experiment stopped, regardless of the number of trials given. We want 60 trials per block.

Then we tried setting condition expression for the number of trials to be less than 60 using a maximum of 48 trials that were coded as being ‘go’ stimulus. This didn’t work either. We end up with too many or too few number of trials. It seems we can’t get it to stick to a certain number of trials even if specified in the condition expression.

Does anyone have any advice on what we are missing/doing wrong??? Alternatively, does anyone have an example of a go-no-go task we could look at?

Thanks you!!

It looks like the Condition Expressions are being set at the block level. Have you tried setting them at the trial level instead?

I have modified the experiment so that the Condition Expression for each trial is set at: Number of Times this trial has been presented is equal to (required number of trials). I have also removed the condition expressions on the blocks.

However, when I run the trial now, the events don’t pop up at all, and it merely skips from instructions to the end of the experiment.

How can I fix it so the trials/events display?

Thanks for your help!


I changed the trial condition expression to:
Number of Times this trial has been presented is less than (required number of trials).

Now the trials display, but it repeats endlessly beyond the stated required number of trials.

Could you please tell me what I’m missing?


I have also attempted to follow the suggestion made in, but that did not work.

Basically, the issue is that the trial blocks are supposed to have 60 trials in each block, with a weighting of 48 trials of Go and 12 trials of NoGo or vice versa, alternating blocks. Unfortunately, I haven’t been able to get any of the blocks to complete 60 trials yet; they usually stop in the 40s and move on to the next block, regardless of changes I make.

Help and advice is very much appreciated!

I think it would be helpful if you posted your experiment. If you go to the File menu, then select, Create an Experiment Package, this will put all your files into a zip.