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Not entirely related to text is the concept of 'chunking'. People are capable of remembering7 plus or minus two pieces of data in their short-term memory. In other words: when someone sees more than 7 pieces of information in one place, one cannot keep it all in memory. If you do a google search for ''chunking usability'' or ''chunking design'' you will find lots of interesting information about this principle. It was discovered nearly a century ago and originally was only considered in relation to physical tasks. It made sense when explaining learning - a set of procedures would become a single chunk after enough repetitoion, thus a more experienced person could do more advanced things because they had chunked collections of simpler things into single units. The same applies to learning information, programming for example. Students spend time writing a function because they have to think of individual lines of code such as printf(), while(), return() but experienced programmers see the whole function as a unit and don't give a second thought to the syntax or basic functions used to implement it. A couple of websites for reading: http://www.chambers.com.au/glossary/chunk.htm and http://www.interaction-design.org/encyclopedia/chunking.html - note how the concept applies to design of presentations.