The concept of Mediation is important for Activity Theory. Since the theoretical traditions have different versions, the concept of Mediation also has different versions. In order to understand the complicated idea, it's better to track the historical development of the notion.  

Mediated Action

The foundation of Activity Theory and CHAT, in general, is Lev Vygotsky’s idea of “mediated action”.

Vygotsky claimed that human action and psychological functions are mediated by tools which refer to technical tools that work on objects and psychological tools that mediate the mind and environment. The idea of “mediated action” is usually represented by a triangle that contains three elements: subject, mediating artifact/tool, and object.

For example, I started the Activity U project on August 19, 2020. Initially, I just made a diagram called “Activity U” which is a test of the “HERO U” framework. I wrote a post to explain the diagram “Activity U”.

The original title of the post is Activity U: The Landscape of Activity Theory. Later, I added “(Part I)” to the end of the title. It expanded from one post to a series of articles. Eventually, a diagram transformed into a Knowledge Curation project!

If we use this model to explain the first stage of the Activity U project, we get the following diagram.

Though the name Activity U refers to Activity Theory and CHAT (Cultural-historical Activity Theory), I also consider other related theoretical approaches for my learning objects. For examples, Vygotsky’s Cultural-historical theory (CHT), Marxism, and practice theories.

Mediating Activity

Lev Vygotsky didn't develop the term "Activity" as a theoretical concept. Activity Theory was initiated by A. N. Leontiev.

According to Nikolai Veresov (2020), “Both CHAT and cultural-historical theory emphasise the importance of cultural mediation in the process of formation of identity as a sociocultural phenomenon. However, they provide different perspectives in relation to what is the basic unit of analysis. For CHAT this unit is a mediated action; cultural-historical theory emphasises dialectical and dynamic aspects by introducing the mediating activities of an individual within changing social environments. In other words, cultural-historical theory is not focused on mediated actions, but on a human being who uses or create cultural tools in order to reorganise the social situation and overcome existing challenges.”

We should pay attention to the difference between “mediated action” and “mediating activities”. For Vygotsky, “Man himself determines his behavior with the help of artificially created stimuli-devices…human behavior was determined not only by the stimuli present, but by a new or changed psychological situation created by the man himself. (Vygotsky 1977, pp. 49–54)”. Thus, the key of the Activity U project is the action of creating and using the HERO U framework and diagram which can be considered as “cultural tools”.

In 2012, Kaptelinin and Nardi summarized five basic principles of Leontiev’s activity theory:

  • Object-orientedness
  • Hierarchical structure of activity
  • Mediation
  • Internalization and externalization
  • Development

According to Kaptelinin and Nardi, "Since the overall focus of Leontiev's approach was on activity, understood as the purposeful interaction of active subjects with the objective world, rather than particular higher mental functions and their ontogenetic development, activity theory is specifically concerned with tools as means that mediate activity as a whole, rather than signs, that is, means that mediate specific mental operations." (p.31, 2012)

It's clear that Leontiev detached from Vygotsky's framework and developed his own approach which emphasizes human work as activity. For Leontiev, mediation means technical tools.

Tool Mediation and Instruments

Some Activity Theorists also use the term "Instruments" to replace the term "Tools" or "Mediating Tool".

As Kaptelinin and Nardi explained, "Tool mediation allows for appropriating socially developed forms of acting in the world. Tools reflect the previous experience of other people accumulated in the structural properties of tools, such as their shape or material, as well as in the knowledge of how the tool should be used. Tools not only shape the external behavior; as discussed below, through internalization, they also influence the mental functioning of individuals. For instance, a person's cognitive map of a city may depend on whether or not the person is a car driver. A software developer understands the abstraction of layers of a software architecture. This understanding is actionable, and he or she does not need to be looking at a diagram of an architecture to use the knowledge in a design task." (p.31, 2012)

We should notice that what Kaptelinin and Nardi talked about is Existing Tools from the cultural context. However, we should notice that a member of a cultural group could make Emergent Tools for his own purpose in order to cope with challenges in his life world.

For the individual level of analysis, we should pay attention to both Existing Tools and Emergent Tools because the former refers to internalization and the latter refers to externalization.

Double Mediation

Some researchers use the concept of Mediation in a broad sense. For example, Yrjö Engeström used the method of "Double Mediation" to develop the Activity System model.

The Activity System (Engestrom, 1987)

The above diagram has a nickname called “Engeström’s Triangle”. It was originally developed by Engeström in his 1987 book Learning by Expanding.

The above Engeström’s triangle is based on the cultural-historical psychologists’ notions of mediation as individual action (subject — instruments — object) at the top of the diagram. Engeström (1987) considered “a human activity system always contains the subsystems of production, distribution, exchange, and consumption.”(p.67), thus, he added the bottom of the triangle to the original individual triangle in order to include other people (community), social rules (rules), and the division of labor between the subject and others.

According to Kaptelinin and Nardi, "The model is a result of a two-step extension of Leontiev's original concept of activity - that is, activity understood as 'subject - object' interaction - to the case of collective activity...Second, it was suggested that each of the three particular interactions within the structure is mediated by a special type of means. Concrete mediational means for these interactions, according to Engeström, are: (a) tools/instruments for the subject-object interaction (as also posited by Leontiev), (b) rules for the subject - community interaction, and (c) division of labor for the community - object interaction." (p.33-34, 2012)


For empirical studies, some researchers put many things under the concept of "Mediated tools" or "Instruments".

I suggest that there is a distinction between Theoretical Concepts and Operational Concepts. Theoretical Concepts are adopted from Meta-theory or Specific Theory. Some frameworks don’t associate with any theories, they only have operational concepts. Operational Concepts are framework-dependent concepts for guiding research and reflection. For example, Yrjö Engeström’s Activity System model is a knowledge framework. Its diagram displays seven operational concepts.

We should notice that a knowledge framework can directly adopt some theoretical concepts as its operational concepts. For example, the above diagram shows “Subject” and “Object” which are core theoretical concepts of Activity Theory. However, some researchers use “Actor” to replace “Subject” with the same diagram for their own work. The concept of “Actor” should be understood as an operational concept. For real-life research, the difference between “Subject” and “Actor” doesn’t matter since we need to see the final data which refers to a person or several people.

While Yrjö Engeström uses the word “Instruments”, other researchers use “Mediating Tool” or similar words. For example, Maral Babapour, Antonio Cobaleda-Cordero, and MariAnne Karlsson adopt Activity Theory to develop a framework for understanding the interrelations between users and workplace design. They use the word “Mediating Tool”.

Resources and Environment?

It seems that Activity Theorists don't pay attention to the concept of "Resources" and the concept of "Environment".

How to deal with these kinds of data in real-life studies from the perspective of Activity Theory?

Some types of "Resources" can be understood as "Object' while other types of "Resources" can be understood as "Instrument". The same method can be applied to "Environment".

Both theoretical concepts and operational concepts can be defined precisely or vaguely. For example, the scope of the concept of “Instruments/Mediating Tool” is very broad in Activity Theory.

The above diagram shows an example, the authors understand “Office Environment” as a “Mediating Tool” from the perspective of Activity Theory. Since Activity Theory doesn’t have a theoretical concept of “Environment,” researchers tend to use the concept of “Instruments/Mediating Tool” to understand “Environment”.

However, if we study the office design activity, we should consider "Office Environment" as the "Object" of the activity.