Zener cards were designed to be used in scientific experiments to attempt to prove the existence of ESP. In the initial experiments, subjects were able to correctly identify the hidden card at rates greater than expected by chance, but further analysis have revealed many possible ways that information could have been exposed such as body language or simply imperfections on the backs of the cards.
I’m much more interested in the ways that people can surreptitiously pass information. This is the main presentation I use for an ESP matching routine. I frame the effect as trying to pass information to and from the volunteer without letting the rest of audience know. It’s fun for everyone watching the volunteer make funny faces rather than the standard routine where the volunteer tries to avoid getting their mind read.
TV networks feel free to contact me about my ESP matching reality dating show idea.