The cards are shuffled each time that they are presented. When you are asked to examine and pay attention to one of the cards, the mind focuses on one particular card without paying much attention to the others because you are also keeping track of the time by counting three seconds. Most people will remember very well the card that they picked, and they will have a general idea of what the other cards looked like, but not in great detail. When a second set of cards is displayed, the card that was selected will seem to have vanished. Several people playing at the same time will find that all the cards that they select will disappear even when each player chooses a different card. The magic happens because our short-term memory is overloaded. Is this really a magic trick or a psychological test?