Hi endrew. I think the best way to do what you want would be to use skip logic. Basically, have the first item in your experiment ask for the participants age. You can set this up using a responses.xls file. Open excel and create a file with the following three headings: variable, value, and skipto. Variable is the name of either a variable that appears in your study (e.g. "age") or a new variable that you want to calculate. Value is the value of that variable. Skipto allows you to specify where the experiment should go next based on the value of a variable. This is what we'll be using. In the skipto field, you'll enter an excel formula that sets up the rules for where in the questionnaire MediaLab should go next based your subjects age.

I've attached a very simply example excel file so you can see this in action. In the example, I made an excel formula that will send subjects to one variable if they are 18, another variable if they are 19, and still another variable if they are 20. In practice, you'd want to continue that logic all the way up to 40. Next, in MediaLab, set a "skipto" value for the final item in each set of 30 clips that sends participants to the next phase of the study rather than having them go on to more sound clips.

That would handle assigning a set of sound clips depending on age. You could use MediaLab's overall condition to assign participants to the "questions" vs. "no questions condition" first, then use this method once they've started to ensure they get the proper list of songs. Note that, for this to work, you'd need to have your age item, all your song clips (for all age groups), and whatever you want subjects to do after the clips contained in one questionnaire file.

I hope that helps I know that might all seem like a lot, so please let me know if it's not clear and I'd be happy to help you create the excel file and integrate into the study.