All information that needs to be attended to has to pass through a channel or
bottleneck in the brain called working memory. This channel has a limited bandwidth; only
a certain quantity of items can be attended to at a time before some of the items are
lost. Psychologists can actually measure the size of this span. When we present
information we need to know how this span works.
When we design web sites, we do not assume that humans can search through unlimited
lists of information nor see everything as it is presented on the screen. Humans
need to see things presented in "chunks" of information small enough to be
processed and stored in their memories. Otherwise, the information is not retained
or recalled later for future use.