I think the FA should be able to 'spot-quiz' any pax who has obviously not being paying attention
Done that!
Back when I first started flying I was standing there in the middle of the cabin and these 2 onboxious men and 1 woman were talking all through the safety demo. I kept giving them evil looks which they saw and sniggered at.
Whilst doing my cabin secure I was debating as to whether I should say something or not (back then I was a mild mannered here to serve cabin crew member - now I am safety safety safety and service is second only after safety) when the decision was made for me, one of the 2 obnoxious guys said "Scuse me, sorry wasn't paying attention before - where is the nearest exit?" I looked at him and for the first time since becoming crew I was a bit rude to a passenger and I said "If you were paying attention just now instead of talking loudly during the safety demonstration which is for YOUR benefit you would know! I know how to get out of here in an emergency so I will be ok. I bet you don't even know where your life jacket is located do you?" (sheepish look and a shaking of head followed) "I bet you don't even know how to activate your oxygen mask in a decompression either!" (again a shaking of head and his 2 companions now were head bowed) I then followed that with "Best hope nothing happens on this flight then hadn't you!" and walked off back to my galley. Passengers seated nearby were sniggering, one or two said "Well done!" and a few winked at me as well.
I will probably get shot down in flames by some SLF now for saying that, but when you are crew it does make you really REALLY angry when people ignore the demonstration!