If a mental picture is used to represent a thought, it needs to be accompanied by a caption, by a set of instructions for how to interpret the picture--what to pay attention to and ignore.Steven Pinker, How the Mind Works pp. 297 (1997).
It is the case, of course, that instructions for use can be remembered and that people can learn to recall almost instantaneously -- very quickly -- the intended use or meaning of at least some images. Consider (some) highway signs containing pictures. Or, chess players, consider a diagram of a chess position (with icons representing the King, Bishop, etc.).
Indeed, my friends, are physical chess pieces different in any pertinent way from "immaterial" icons representing chess pieces? "Real" chess pieces and "real" chess boards also don't usually carry captions describing how chess pieces can be played.