According to a CMU study by Lynne Reder, "our ability to associate something to a context depends on it being a 'chunk' or unit".Chunking" occurs when otherwise unrelated items are perceived as a unit".
"For example, the three-letter combination FBI—but not, say, SVQ or TMY,is chunked because it's associated with an entity, and we hear the grouping so often. Items that are chunked take up less of our mental resources to encode since each item doesn't have to be encoded separately. -Abstract pictures were harder to remember than words: "From a common sense perspective, you might think that if something's unfamiliar, then it should really stand out in your memory, and you might remember it better," he said. "On the other hand, a more sophisticated view is that if the different parts of a stimulus don't cohere in some sense, it'll be harder to recover them."
http://www.seedmagazine.com/news/2006/08/how_we_make_a_memory.php
