These cards are cards used to conduct experiments for extrasensory perception and clairvoyance.
There are 25 cards in the deck five of each. On every card there is one of five symbol. A hollow circle (one curve) a Greek cross (two lines) three vertical wavy lines (or "waves") a hollow square (four lines) and a hollow five-pointed star.
You can test your friend. Sit in front of him or her. Observe the symbol on the card. Focus on it. Telepathically send the image to your friend. Enter the answer.
You can also test yourself by guessing symbol is on the outer side.

After you go trough entire deck you will see how results.