Is it possible to have some trials occur more frequently?

rudale

Hello,

I am programming a cueing paradigm, following the beginners tutorial. In the tutorial, all conditions occur equally frequently. If I wanted 'valid' trials to occur 80% of the time and 'invalid' to occur 20% of the time, is there a way to do this?

sebastiaan

Hi,

Yes, you can use the weight operation of the loop item, which is described here:

• http://osdoc.cogsci.nl/3.1/manual/structure/loop/#weight

Essentially, you create a column, say w, that indicates how often a particular should be repeated; in your case that would be 4 for valid trials, and 1 for invalid trials, resulting in an 80%/20% ratio. And then you add a line weight w to the script of the loop item.

Does that make sense?

Cheers,
Sebastiaan

rudale

Yes that makes perfect sense, thank you!

stm

Hi,

I am using a similar paradigm (different % of valid/invalid trials) and included the weight function accordingly. Additionally, I'd like to randomize the sequence of all trials. Currently, the trials as defined in the rows of the loop-table are randomized but if I apply a weight to a row (e.g. 4), the trial defined in that row is always repeated 4 times in sequence.

Example:

word weight

bunny 1

carrot 4

The list [bunny, carrot] is shuffled but I want the list [bunny, carrot, carrot, carrot, carrot] to be shuffled. Is that possible without major changes of my loop-table?

Best, Stefanie

sebastiaan

Hi Stefanie,

Yes, you can do that by adding a shuffle operation after the weight operation! See also:

• https://osdoc.cogsci.nl/3.2/manual/structure/loop/

Cheers!

Sebastiaan