We use a number of tracking mechanisms - including IP address detection - to ensure that no participant takes part in a study more than once. To increase data fidelity, we make participants verify their accounts via email address and phone number, and we use these to run checks on their accounts.
Additionally, we perform regular checks on our participants using a range of mechanisms to detect any suspicious activity and maximize the quality of our pool - these help us catch the occasional bad apple.Â
For more information on how we monitor our participant pool for bots and other suspicious activities, see this blog.