How is a work of art altered by our looking at it?

An excerpt from "Art Current: The Portland Museum of Art Biennial" by Brita Konau, published by The Free Press:

"Eggert's interactive piece I at first thought just artfully cute. On a black panel, small levers are set in motion, through proximity sensors, to spell out the title of the piece, "Wonder." Upon further reflection though, I came to appreciate the questions this work asks. How is a work of art altered by our looking at it? How are we changed? Is physical observation replaceable by perusal of reproductions? Can that still instill the same reaction, the same "wonder"? Questions that have not gone away since Walter Benjamin reflected on "The Work of Art in the Age of Mechanical Reproduction." For me the showstoppers are not the large, site-sensitive installations. Rather, they are the quiet, sophisticated works that ask you to look closely and spend contemplative time with them."