A famous ESP experiment at the Duke University was performed by Lucien Warner and Mildred Raible. The subject was locked in a room with a switch controlling a signal light elsewhere, which she could signal to guess the card. Ten runs with ESP packs of cards were used and she achieved 93 hits (43 more than chance). Weaknesses with the experiment were later discovered. The duration of the light signal could be varied so that the subject could call for specific symbols and certain symbols in the experiment came up far more often than others which indicated either poor shuffling or card manipulation. The experiment was not repeated.