Zener Cards

Zener cards (ゼナー・カード) also known as ESP cards are cards used in System Scans, most specifically, clairvoyance.

Background
Perceptual psychologist Karl Zener designed the cards in the early 1930s for experiments conducted with his colleague, parapsychologist J. B. Rhine.

In Toaru Majutsu no Index, the card's material was changed from vinyl to ABS resin, that was instituted by the United States of America in 1992, due to a trick that the fingerprints on the card make it possible to figure the card's contents.

Appearance
There are five different Zener cards: 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. There are 25 cards in a pack, five of each design.

The esper being tested must be able to determine what the contents of the card is correctly.

Sisters Arc

 * Main article:Sisters Arc

In Tsukuyomi Komoe's supplemantary lessons, she gives a lecture of the history of the ESP Card to an unenthustiastic Kamijou Touma.

Three Stories Arc

 * Main article:Three Stories Arc

In the anime adaptation, cards are shown in Touma's coffee table during his attempt at finishing his summer homework.

Level Upper Arc

 * Main article:Level Upper Arc

In the System Scan of the anime adaptation of Toaru Kagaku no Railgun, a clairvoyant or a telepath is being tested using the ESP Card.