Millisecond Forums

Randomizing paired blocks of images

https://forums.millisecond.com/Topic13803.aspx

By beccabos - 7/17/2014

Hello,

I'm trying to program a choice task- I have three categories of images, that I've paired with each other in three blocks (Ha, Hb, Ub).

Is there a way to randomize the presentation of all of these images… e.g., an equal likelihood that a pairing from any of these blocks will be presented next, instead of randomized sequentially by three separate blocks? I am not sure how to organize the trials to do this as they're currently set up… would I have to move all of the pairs to a single block to do that? Part of the current script is attached here. 

Thanks for the help!

Best,
Becca
By Dave - 7/17/2014

There are no <block> elements at all in the code you attached. There are only three different <trial> elements -- <trial choicetrial_d1> to <trial choicetrial_d3> -- each apparently sampling from a given pair of stimulus elements -- <picture CATstrat_d1>/<picture CAT_d1> to <picture CATstrat_d3>/<picture CAT_d3>. There are 36 item pairs per category.

Thus it should be as simple as doing

<block myblock>
/ trials = [1-108 = noreplace(choicetrial_d1, choicetrial_d2, choicetrial_d3)]
</block>

which will give you 36 d1-trials, 36 d2-trials and 36 d3-trials in random order.

If that's not what you are aiming for, please clarify.
By beccabos - 7/17/2014

This is SO helpful, Dave- thank you!!! I really appreciate it… this is exactly what I was missing.