In semiotics, a sign whose meaning derives from the connexion of one thing with another through a cause and effect relationship, such as footprints being the index of a certain animal's prior presence, or as the "index" hand of a watch signals the passage of time. In art, an indexical mark or object is one that signifies the action of an artist, such as the brushstroke of an abstract expressionist painter, or the presence of a found or "ready-made" object being the index of an artist's activity in choosing and displaying it.