Let's let The Paris Review give you the backstory:
In 1963, a sixteen-year-old San Diego high school student named Bruce McAllister sent a four-question mimeographed survey to 150 well-known authors of literary, commercial, and science fiction. Did they consciously plant symbols in their work? he asked. Who noticed symbols appearing from their subconscious, and who saw them arrive in their text, unbidden, created in the minds of their readers? When this happened, did the authors mind?
Of the 150 authors McAllister solicited, 75 wrote back, and most offered the youngster some substantive thoughts. Over at The Paris Review, you will find replies by Jack Kerouac, Ayn Rand (above), Ralph Ellison, Ray Bradbury, John Updike, Saul Bellow, and Norman Mailer. Not bad for a kid who sent out a form letter ... and never bothered to send a thank-you letter.