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98 Chapter 3 Understanding users

(Hutchins, 1995). A central goal has been to look at how structures in the environ-
ment can both aid human cognition and reduce cognitive load. A number of alter-
native frameworks have been proposed, including external cognition and
distributed cognition. In this chapter, we look at the ideas behind external cogni-
tion-which has focused most on how to inform interaction design (distributed
cognition is described in the next chapter).

3.4.3 External cognition

People interact with or create information through using a variety of external rep-
resentations, e.g., books, multimedia, newspapers, web pages, maps, diagrams,
notes, drawings, and so on. Furthermore, an impressive range of tools has been de-
veloped throughout history to aid cognition, including pens, calculators, and com-
puter-based technologies. The combination of external representations and physical
tools have greatly extended and supported people's ability to carry out cognitive ac-
tivities (Norman, 1993). Indeed, they are such an integral part that it is difficult to
imagine how we would go about much of our everyday life without them.
External cognition is concerned with explaining the cognitive processes involved
when we interact with different external representations (Scaife and Rogers, 1996).
A main goal is to explicate the cognitive benefits of using different representations
for different cognitive activities and the processes involved. The main ones include:
1. externalizing to reduce memory load
2. computational offloading
3. annotating and cognitive tracing

1 . Externalizing to reduce memory load
A number of strategies have been developed for transforming knowledge
into external representations to reduce memory load. One such strategy is exter-
nalizing things we find difficult to remember, such as birthdays, appointments, and
addresses. Diaries, personal reminders and calendars are examples of cognitive ar-
tifacts that are commonly used for this purpose, acting as external reminders of
what we need to do at a given time (e.g., buy a card for a relative's birthday).
Other kinds of external representations that people frequently employ are
notes, like "stickies," shopping lists, and to-do lists. Where these are placed in the
environment can also be crucial. For example, people often place post-it notes in
prominent positions, such as on walls, on the side of computer monitors, by the
front door and sometimes even on their hands, in a deliberate attempt to ensure
they do remind them of what needs to be done or remembered. People also place
things in piles in their offices and by the front door, indicating what needs to be
done urgently and what can wait for a while.
Externalizing, therefore, can help reduce people's memory burden by:
reminding them to do something (e.g., to get something for their mother's
birthday)