"Alois Riegl, of the Vienna School of Art History in 1900. . . understood that art is incomplete without the perceptual and emotional involvement of the viewer. Not only does the viewer collaborate with the artist in transforming a two-dimensional likeness on a canvas into a three-dimensional depiction of the world, the viewer interprets what he or she sees on the canvas in personal terms, thereby adding meaning to the picture. Riegl called this phenomenon the 'beholder's involvement' or the 'beholder's share.'
Art history was now aligned with psychology. Ernst Kris and Ernst Gombrich, two of Riegl's disciples, argued that a work of art is inherently ambiguous and therefore that each person who sees it has a different interpretation. In essence, the beholder recapitulates in his or her own brain the artist's creative steps."
— Eric R. Kandel, What the Brain Can Tell Us About Art, The New York Times