19. Gulf of Evaluation and Gulf of Execution
The term 'Gulfs of Evaluation and Execution' were introduced in Norman (1986) and popularised by his book, The Design of Everyday Things (Norman 1988), originally published as The Psychology of Everyday Things.
The Gulf of Execution
The gulf of execution is the degree to which the interaction possibilities of an artifact,
a computer system or likewise correspond to the intentions of the person and what that person perceives
is possible to do with the artifact/application/etc. In other words, the gulf of
execution is the difference between the intentions of the users and what the
system allows them to do or how well the system supports those actions (Norman
1988). For example, if a person only wants to record a movie currently being
shown with her VCR, she imagines that it requires hitting a 'record' button. But
if the necessary action sequence involves specifying the time of recording and
selection of a channel there is a gulf of execution: A gap between the
psychological language (or mental model) of the user's goals and the very
physical action-object language of the controls of the VCR via which it is
operated. In the language of the user, the goal of recording the current movie
can be achieved by the action sequence
"Hit the record button," but in the
language of the VCR the correct action sequence is:
1) Hit the record
2) Specify time of recording via the controls X, Y, and Z.
channel via the channel-up-down control.
4) Press the OK button.
Thus, to measure or determine the gulf of execution, we may ask how well the
action possibilities of the system/artifact match the intended actions of the
In the rhetoric of the GOMS model (see this), bridging the gulf of execution
means that the user must form intentions, specify action sequences, execute actions,
and select the right interface mechanisms (GOMS stands for Goals, Operators,
Methods and Selection Rules).
The Gulf of Evaluation
The gulf of evaluation is the degree to which the system/artifact provide
representations that can be directly perceived and interpreted in terms of the
expectations and intentions of the user (Norman 1988). Or put differently,
the gulf of evaluation is the difficulty of assessing the state of the system
and how well the artifact supports the discovery and interpretation of that
state (Norman 1991). "The gulf is small when the system provides information
about its state in a form that is easy to get, is easy to interpret, and matches
the way the person thinks of the system" (Norman 1988: p. 51).
Thus, if the system does not "present itself" in a way that lets the user derive which
sequence of actions will lead to the intended goal or system state, or derive
whether previous actions have moved the user closer to her goal, there is a
large gulf of evaluation. In this case, the person must exert a considerable
amount of effort and expend significant attentional ressources to interpret the state of the system
and derive how well her expectations have been met. In the VCR example from
above, the design of the controls of the VCR should thus 'suggest' how to be
used and be easily interpretable (e.g. when recording, the 'record' control
should signal that is is activated or a display should).
To sum up, the gulfs of evaluation and of execution refer to the mismatch
between our internal goals on the one side, and, on the other side, the
expectations and the availability of information specifying the state of the
world (or an artifact) and how me may change it (Norman 1991).
The idea that the discrepancy between user and system should be conceived of gulfs came from Jim Hollan and Ed Hutchins during a revision of a chapter on direct manipulation in the book User-Centered System Design (1986).
Donald Norman's writings must be understood within the theoretical framework
of information-processing cognitive psychology. The fundamental ontological and
epistemological assumptions of this paradigm, as well as some of its methods,
are considered very problematic by many. As such, Norman's theories described
above are subject to many of the criticisms that have been raised against the
information-processing approach to human cognition.