We got a good question from a teacher named John Fawsitt about Captur paddles on the ETJ mailing list:

I used to use 4 cards 1, 2, 3, 4 to do the same thing (as Captur Paddles) for large classes. Mostly when I was working from a text book to answer the multiple choice questions. Got a good reaction until some guys started to actually play cards with them. Can't the students see the backs of the other students' paddles thereby leading to some herd bahviour? Or do you do a "1,2,3 up!" sort of synchronising their replies?

Here's my reply:

Students can see the backs if the paddles are held high, which is why a lot of the early research on flashcard answer systems had blank backs. I try to lessen the chances of mimicry by (1) doing what you said, a synchronizing count-down; and (2) asking them to hold the paddles close to their faces, instead of high in the air or up over their shoulders.

I think the concept of a count-down is familiar to my Japanese students, because they've seen the "batsu maru" (x and o) paddles used on Japanese TV variety shows, and they may have even used these batsu maru paddles themselves at some point.

I also tell them to hold these paddles so that their hands are covering the bottom, so that all I can see is the one answer (A, B, C or D) that they want to show me. This makes it easier for me to see all of the answers at a glance in large classes.