The Art of Icons
http://www.humanfactors.com/downloads/aug07.asp#kath

Michaels, Mary M.
UI Design Newsletter
2007

Abstract:

Being "minimalist" and "streamlined" is not always most effective. Have you ever written yourself a quick, shorthand note, only to find later that you had no way to unpack your own great idea? Icons work similarly. They are pictures – meant to provide a visual shorthand to users moving through a task. While research indicates that icons are best when initially paired with text to increase recognition and learnability, users experienced with a given set of icons will begin to ignore the text, scanning for and acting from the image alone.