Here is a short little blurb about memory and design. In brief, the article explains that imagery was at one point the only way people could communicate. Written language is a relatively modern invention when taking the entire span of human life into account. Even after written language was developed, many people were illiterate, so symbolic imagery was needed to communicate with the masses. Images are closely associated with memory because that is how we distinguish what the image means and the context that surrounds it.
Link to the article: http://www.sebastianguerrini.com/features/memory-and-design/
