Activity Theory

Origin. Lev Vygotsky's cultural-historical psychology (1920s-1930s); developed by Alexei Leontiev (1940s-1970s); extended by Engeström (1987) into organizational analysis.

Mechanism. Human activity is mediated by tools (physical and symbolic) and is always directed toward an object. The unit of analysis is not the individual but the activity system: subject, object, tools, rules, community, and division of labor. Contradictions within and between activity systems drive development. Understanding behavior requires understanding the entire activity system, not just the individual actor.

Procedure. Identify the activity system: who is the subject? What is the object (the thing being transformed)? What tools mediate the transformation? What community shares the object? What rules govern the activity? How is labor divided? Map the relationships. Identify contradictions — tensions within or between components. Contradictions are sources of both problems and development. Intervene by resolving contradictions or by redesigning mediating tools.

Applies to. Work analysis, technology design, organizational change, understanding failures in human-tool-environment systems.

Limitations. Activity systems are analytical constructs; drawing the boundary around "the system" is a design choice that shapes what is visible. The framework is descriptive rather than predictive — it explains retrospectively but does not predict outcomes. Also: the concept of contradiction can become so flexible that any tension is a contradiction, diluting the analytical power.