Screening AMT participants from previous studies

Sometimes, you want to make sure some AMT workers, who took one of your previous studies, cannot take your current study. We found a way to do that using a simple script on AMT and a pre-screening survey on Qualtrics. More details in this post on the Experimental Turk blog. 

Update: You can also use Qualifications on AMT as detailed here - https://experimentalturk.wordpress.com/2015/02/18/excluding-mturk-workers-who-participated-in-your-previous-studies-an-excel-solution/