Cognitive Dimensions


T.R Green, Marian Petre, Alan Blackwell


“A broad-brush evaluation technique for interactive devices and for non-interactive notations. It sets out a small vocabulary of terms designed to capture the cognitively-relevant aspects of structure, and shows how they can be traded off against each other .” [2]


1989 - Present


A method was needed that allowed designers without extensive cognitive science training to critically evaluate the usability of their designs (information artifacts) and discuss the tradeoffs that occur based on design decisions.

Cognitive Dimensions
Introduction & Purpose

Cognitive Dimensions, or more formally, the Cognitive Dimensions of Notations theory is a framework for evaluating the usability of information artifacts originally developed by T. R. Green in 1989. [1]

Marian Petre and Alan Blackwell are two additional HCI researchers who have helped to support the development and application of the Cognitive Dimensions framework.

Petre teamed up with T. R. G. Green in 1996 to further refine the Cognitive Dimensions Framework. [2]

Alan Blackwell has worked with T. R. G. Green to develop tutorials and questionnaires to help make Cognitive Dimensions more easily usable for HCI practitioners.[3]

Cognitive Dimensions continues to be used today by usability practitioners and designers (for example, a recent study utilized the Cognitive Dimensions Framework to evaluate constraint diagrams [4]).

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

Theory Origin

In a study of office workers, Lucy Suchman demonstrated that expert help systems designed using an idealized user model were ineffective at helping users who were having difficulty accomplishing a complex task. Using ethnographic methods of observation and interviews in office settings, the approach revealed frequent & large discrepancies between how users used computer technology and how designers of software technology envisioned users would use technology. Novice users couldn’t follow the preconceived procedures, and instead interacted based on current situation. [1]

Detailed accounts

Similar to ethnomethodology, Situated Action approach provides detailed accounts of how technology is used by people in different contexts [1]. Ethnographic methods are used to generate these accounts using extensive observations & interviews for each setting.

Design recommendations

Situated Action promotes designing systems that can match the way people behave and use technology [1]. Instead of designing systems with preconceived models of how people should interact with computers, systems should be designed to match the way people behave & use technology.

Situated Action Approach

Situated Action studies the relations between people and their circumstances to achieve intelligent action. [1] Intuition and interpretation are essential elements humans use to execute on a plan, as context is ever changing. People don’t always interact with technology according to idealized user models, as Suchman found while observing office workers. To explain this discrepancy, Situated Action theorized that computers and other aspects of the environment affect the user’s agency, that agency emerges from relation between human and machine in different ways depending on setting; A person’s or thing’s agency is reconfigured when it comes into contact with another person or thing. While people may have plans of action in mind, their actual action may diverge depending on what is actually happening in a specific situation. In the case of office workers, humans use plans in context and improvisationally as one among many guides to action.