The 14 Different Dimensions [3]

Abstraction Gradient

Types and availability of abstraction mechanisms (Is there a way to create new definitions?)

Closeness of Mapping

Closeness of representation to domain (How close is the notation to the result it is trying to describe?)


Similar semantics are expressed in similar syntactic forms (Are there different parts that mean the same?)


Verbosity of language (Is it long-winded or brief?)


Notation invites mistakes (Are some kinds of mistakes common? Do you often make mistakes?

Hard Mental Operations

High demand on cognitive resources (Does the design require complex or difficult processes to work out?)

Hidden Dependencies

Important links between entities are not visible (Are impacts of change visible?)

Premature Commitment

Constraints on the order of doing things (Can you do your work in the order you prefer?)

Progressive Evaluation

Work-to-date can be checked at any time (Can you stop in the middle of work to evaluate your work?)


Degree of commitment to actions or marks (Can you "play around" with ideas before committing them?)


The purpose of a component is readily inferred (Do you understand what each part does?)

Secondary Notation

Extra information in means other than formal syntax (Is it possible to make notes or attach additional info?)


Resistance to change (Is it easy to make changes to previous work? Is it adaptable?)


Ability to view components easily (Can you locate different parts easily? Can you see the big picture?)

Cognitive Dimensions
The Cognitive Dimensions

The 14 Cognitive Dimensions serve as heuristics for the designer or user to use to help them evaluate the system.


In order to understand the context of usage for these dimensions, it is also important to provide some basic definitions that relate to the use of Cogntive Dimensions [5].

System: The design that is being evaluated. T. R. G. Green originally defined the system as an information artefact, of which it could be an interactive artefact (such as a word processor or mobile phone) or a non-interactive artefact (such as a graph or programming language).

Product: The end result or object that is created via the usage of the system.

Notation: This is the means through which the user communicates with the system. It is the various components found within the system and can include text interfaces, pictures, touch controls, audio controls, etc.

Sub-Devices: Exceptionally complex systems might include secondary notations that help the user successfully operate the system. These may be helper devices (like notes next to your computer) or redefinition devices (like keyboard hotkeys, personalized controls, etc.).

Activity Theory

Activity theory is a conceptual framework originating from the socio-cultural tradition in Russian psychology. Since the early 1990s, Activity Theory has been applied in Human Computer Interaction (HCI) and evolved into one of the most noteworthy theories in the field. It focuses on the purposeful interaction between the "subject" and the "object".

"Activity," the foundational concept of activity theory, is understood as a relationship between the subject, (that is, an actor) and the object, (that is, an entity objectively existing in the world. A common way to represent Activity Theory is "S < - > O." [2]

Activity Theory
Contributions to HCI

In general, activity theory contributions to the field of HCI have been of the following three types:

1. Theoretical re-framing of some of the most basic HCI concepts. [2]

2. Providing conceptual tools for design and evaluation. [2]

3. Serving as a theoretical lens in empirical studies. [2]

There are two major versions of activity theory: the approach developed by Leoniev, and a closely relatied approach proposed by Engeström. By "activity theory” in general we mean an aggregated framework comprising a combination of these two approaches. [2]

Situated Action


Lucy Suchman


Situated Action studies the relations between people and their circumstances to achieve intelligent action. While people may have plans of action in mind, their actual action may diverge depending on what is actually happening in a specific situation. [1]


1987 (Publication of Plans and Situated Action book)


Represents an important, principled, and successful attack on classical cognitive-science based theories of human-computer interaction. The reconceptualization of role of plan in human-computer interaction widely influenced and field of Science and Technology Studies (STS), Computer-Supported Cooperative Work (CSCW), Artificial Intelligence, Cognitive Science, and HCI. [2]

Influences modern practices of ethnography-based usability testing and evaluation.

Situated Action
Introduction & Purpose

Situated Action traces it’s roots to Lucy Suchman’s Plans and Situated Action book. Influenced by cultural anthropology, Situated Action approach offers detailed, ethnographic accounts of how humans use technology differently in different contexts, illustrating how they can be different from the ideal plans conceived by the technology designer. [1]

As a theoretical lens, Situated Action describes and explains human-computer interactions, without attempting to predict user performance or prescribe guidance for design.