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Causal Mechanisms in Complex Evaluations

With the analysis of causal mechanisms, we examine not only whether a programme works, but how and why/why not, in order to make programmes more effective. In this project, we aim to pool experience of causal mechanism approaches in complex evaluations and advance the methodological debate.

What are causal mechanisms?

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Causal mechanisms explain what is going on between the intervention and the outcome. They generate the observed outcome, enable evaluators to disentangle the effects of an intervention and answer questions about how and why.

Given the complexity of programmes and diversity of evaluation questions, evaluators make a great effort to open the ‘black box’ and uncover the causal mechanisms between intervention and impact. In the area of international development cooperation, programmes are often particularly multifaceted, are implemented indirectly through partner organisations, take place in varying contexts and are frequently subject to changes and delays. As a rule, evaluators also address a large number of evaluation issues. This includes considering to what extent a programme has achieved results and how or why a programme does or does not work.

The objective of this research project is to pool experience of causal mechanism approaches in complex evaluations and continue the debate about methodology. We would like to invite you to take part in the discussion on mechanisms. Just contact us and tell us about your experience of working with causal mechanisms.

Causal mechanisms in complex evaluations

It is particularly helpful in complex evaluation situations to examine causal mechanisms. At the core of working with causal mechanisms is the systematic analysis of basic interrelations between (elements of) an intervention and its expected outcomes. In formative evaluations, mechanisms can provide a better understanding of the way in which complex programmes are implemented. In summative evaluations, analysing causal mechanisms enables the evaluator to arrive at more credible statements on the causal links between an intervention and the observed outcomes.

However, the concept of causal mechanisms is applied differently across evaluation approaches. Mechanisms are described as causal processes in process tracing, contribution analyses and other theory-of-change approaches. Applying a broad analytical focus, they describe the entire causal process between intervention and outcomes. In the realist evaluation approach, by contrast, evaluators use what we call context-mechanism-outcome configurations. In this case, the intervention triggers or hinders the behaviour-changing mechanism. Looking for behavioural and psychological explanations, statistical procedures such as the meditation analysis examine “social mechanisms”, which they model and test as intervening variables. Moreover, causal mechanisms are also relevant in experimental designs, which make it possible to investigate the impacts of different elements of an intervention by varying the treatment arms.


Portrait von Dr. Johannes Schmitt
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Dr Johannes Schmitt

Senior Evaluator - Team Leader

Phone: +49 (0)228 336907-946


[Translate to Englisch:] Portrait Sven Harten
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Dr Sven Harten

Head of Competence Centre for Evaluation Methodology / Deputy Director

Phone: +49 (0)228 336907-950


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