Figure 1: The gulfs of execution and evaluation according to Norman (adapted from [Norman 1986])

Figure 1: The gulfs of execution and evaluation according to Norman (adapted from [Norman 1986])

Figure 2: The execution bridge according to Norman (adapted from [Norman 1986])

Figure 2: The execution bridge according to Norman (adapted from [Norman 1986])

Figure 3: The evaluation bridge according to Norman (adapted from [Norman 1986])

Figure 3: The evaluation bridge according to Norman (adapted from [Norman 1986])

Donald Norman's theory of action describes how system state is interpreted and manipulated by humans.

17.03.2026

“Technology may change rapidly, but people change slowly. The principles [of design] come from understanding of people. They remain true forever.”
(Donald A. Norman)

Donald A. Norman’s theory of action offers a foundational framework for understanding how people interact with technical systems. At its core, the theory argues that human action is shaped by a gap between how users formulate their goals and how systems represent their operations. A person’s goals are expressed in psychological terms, that is, in forms that are meaningful from the user’s perspective. By contrast, the mechanisms and states of a system are expressed in physical terms, which correspond to the technical structure and operation of the system itself.

This discrepancy between psychological and physical terms gives rise to many of the central challenges of design, analysis, and use. Whereas users think in terms of desired outcomes, systems require interaction through controls, states, and physical mechanisms. Norman’s model is especially valuable because it makes this discrepancy visible and shows how effective design can help bridge it.

The Gulf of Execution and Evaluation

Norman conceptualizes this discrepancy through two key ideas: the Gulf of Execution and the Gulf of Evaluation. Together, these gulfs describe the distance between a user’s internal goals and the external behavior of a system.

The Gulf of Execution refers to the difficulty users may experience when trying to translate their goals and intentions into executable actions. Even if a user knows what they want to achieve, it may not be obvious how the system allows that goal to be carried out.

The Gulf of Evaluation, by contrast, refers to the difficulty of understanding the system’s response. After acting, the user must be able to perceive and interpret the resulting system state in order to decide whether the intended goal has been achieved.

As illustrated in Figure 1, these two gulfs form the conceptual core of Norman’s theory. They help explain why interaction problems often emerge either because users cannot determine how to act or because they cannot understand what the system has done in response.

The Execution Bridge

The Execution Bridge describes the movement from internal intention to external action. It captures the process by which a user attempts to transform a desired outcome into manipulations of the system’s physical mechanisms.

As shown in Figure 2, the bridge represents the transition from psychological goals to physical operations.

Goals and intentions

A goal is the state a person wishes to achieve. An intention is the decision to act in such a way as to bring about that goal. This distinction is important because users do not interact with systems without purpose; their actions are guided by deliberate attempts to reach meaningful outcomes.

Action specification

The next step is action specification. This is the psychological process of determining the representation of the actions that are to be executed by the user on the mechanisms of the system. In other words, the user develops a plan for how the intended goal can be translated into concrete operations.

Interface mechanisms

These planned operations are then carried out through interface mechanisms, the physical devices through which users interact with and influence the system’s physical variables. Buttons, switches, menus, touch interfaces, and other input elements can all function as such mechanisms.

The Evaluation Bridge

The Evaluation Bridge describes the reverse movement: from the system’s physical state back to the user’s understanding of what has occurred. If the Execution Bridge is concerned with doing, the Evaluation Bridge is concerned with making sense of the system’s response.

As illustrated in Figure 3, this bridge emphasizes the importance of feedback, perception, and interpretation in successful interaction.

Mapping between the physical mechanisms and system state

A crucial aspect of evaluation is the mapping between the physical mechanisms of the system and the resulting system state. This mapping describes the relationship between the settings of the mechanisms and the condition of the system itself. Clear and intuitive mapping supports understanding, whereas poor mapping makes system behavior harder to interpret.

Interpretation of system state

The relationship between the physical state of the system and the psychological goals of the user cannot be grasped directly. Instead, the user perceives the system through the interface display, which presents relevant aspects of the physical system state in a form that can be observed and interpreted. Through perception, this displayed information is translated into a psychological representation. Subsequently, the perceived system state is interpreted in terms of the psychological variables that are relevant to the user’s goals.

Evaluating the outcome

Evaluation of the system state requires comparing the interpreted perceived state with the desired goals. This comparison is not merely a final judgment; it often generates a revised or entirely new set of goals and intentions, thereby continuing the cycle of interaction.

Why This Theory Matters for Design

Norman’s theory of action remains influential because it provides both a conceptual and practical way of understanding usability. Many design problems can be traced back to one of the two gulfs: users may struggle to determine how to act, or they may struggle to understand the system’s feedback after acting.

For this reason, the theory is highly relevant to the design of interactive systems. Effective design reduces the gulfs by making possible actions more visible, mappings more intuitive, and system states easier to perceive and interpret. In this sense, Norman’s theory does not merely describe interaction; it offers a powerful lens for designing systems that better align physical mechanisms with human goals.

References

Norman, D. A. (1986). Cognitive engineering. In D. A. Norman & S. W. Draper (Eds.), User centered system design: New perspectives on human-computer interaction (pp. 31–61). Hillsdale, NJ: Lawrence Erlbaum Associates. https://doi.org/10.1201/b15703-3

Disclosure Statement

This text was prepared with the assistance of the AI language model GPT-5.4, which was used for drafting and linguistic revision. The author defined the content requirements and remains responsible for the final version.