Introducing User-Centered Systems Design - Foundations for Designing User-Centered Systems - page 23

Fig. 1.5 A representation of
the ACT-R cognitive
architecture with the SegMan
extension to allow it to
interact with interfaces
through computer bitmaps

ACT-R

Declarative
Buffer

Goal
Buffer

Production
Rule System

Motor
Buffer

Perceptual
Buffer

Image
Processing
Routines

Simulated Eyes
and Hands

Motor
Routines

Computer Environment

This perceptual buffer represents many of the aspects of the human vision system.
Similar buffers should be created for hearing and the other senses.
At the center of the architecture is a reasoning system that can access information
in the perceptual buffer and access and modify information in the declarative
memory and goal buffers. It uses the information in these buffers to guide its
processing, using a process that mimics human behavior. Output actions to the
external world are put into a motor buffer, where motor routines generate the results.
This representation is somewhat generic and far from complete, but illustrates a
theory of the major information processing components of the user. There are other
theories of how users process information, and even the ACT-R theory has changed
over time. Work is ongoing to apply this approach to create models of users that
can be used to test interfaces (e.g., Byrne 2001 ; Freed and Remington 2000 ; Ki-
eras et al. 1997 ), to serve as intelligent colleagues (Weiland et al. 2002 ) and
opponents in computer-based games and simulations (e.g., Jones et al. 1999 ; Laird
and van Lent 2001 ; Tambe et al. 1995 ), and to summarize our knowledge of human
behavior (e.g., Anderson et al. 2004 ; Jones et al. 2000 ; Lovett et al. 2000 ).

1.6 Summary

This chapter has introduced the study of people who use artifacts (i.e., users),
given you some definitions and useful terms, and provided an overview to organize
your further reading. We have also highlighted some common (mistaken) pre-
conceptions about what makes for good design and noted why studying users is
important. In particular, we have introduced the concept of the fundamental
attribution error of design, where designers think that users are like themselves,
which is very often not the case.