Hello,

I´m currently adapting the Alcohol Dot Probe Script the way I want my experiment to work.

I need help on how to compute a variable inter-trial interval. I want the inter-trial trial to vary randomly between the three values 500, 1000 and 1500ms. 
In the script the inter-trial value is set to 0 ( <values> /iti=0 </values> ) and integrated in the trial via the posttrialpause attribute (/posttrialpause = values.iti)

How can I compute the variable inter-trial interval? 

What I tried so far:
Created a list that randomly selects one of the three iti-durations
</list itidurations
/ items = (500, 1000, 15000)
/replace = true
</list>

I tried a few things but cannot figure out how to integrate it into the trial element. 

Thanks a lot in advance.

Best regards, 
Leni

In the <trial> elements, do

/ ontrialbegin = [values.iti = list.itidurations.nextvalue]

i.e., sample a value from the <list> you specified and store it in the global variable values.iti

Leave

/ posttrialpause = values.iti

as is.