Behavior change is extremely hard. Or rather, behavior change experts are only involved for behavior change challenges that others have failed at repeatedly, which boils down to the same thing when it comes to behavior change intervention development. Because this is complicated, a series of tools has been developed to assist with different aspects of the intervention development process. This vignette shows how decisions taken when applying two such tools can be documented using justifier: Intervention Mapping and the Behavior Change Wheel.

In theory, each of these development processes is underlied by a wealth of insights and lessons about the many choices that have to be made during the intervention development procedure. Yet, in the individual intervention development processes, the decisions that are taken and their justifications are often poorly documented. This prohibits learning many potential lessons from such processes.

The justifier package offers a solution to this situation. It provides a standard for documenting decisions and their justifications using a format that can easily be integrated in text files, such as meeting minutes. The format is simultaneously human-readable and machine readable. The latter enables automatically reading all justifications in a project into a software package for further processing.

By applying justification frameworks, the decisions and underlying justifications can be categorized, enabling automatically extracting all decisions and justifications that are relevant to, for example, a given phase in intervention development. This facilitates learning from intervention development in practice without first requiring coding of, for example, minutes.

Intervention Mapping

The first tool is the Intervention Mapping protocol. It can be used for intervention development, analysis (and potentially improvement or adaptation) of existing interventions, and for description of the intervention development process or products. It is extremely comprehensive, which is at once one or its core strengths and main weaknesses. On the one hand, if one follows the Intervention Mapping protocol, one is assured of a very thorough development process, where all decisions are solidly informed by theory and evidence. On the other hand, exactly because of this, Intervention Mapping is often perceived as unwieldy and too slow to follow in practice. Nonetheless, Intervention Mapping has been used for the development of a large number of interventions ( lists around 1000 articles describing around 300 interventions).

A very rough picture of the structure of Intervention Mapping can be painted by the six ‘steps’ that are iteratively and nonlinearly applied:

  1. Needs assessment: obtaining a comprehensive overview of the problem, needs, and capacities
  2. Logic model of the behavior: mapping the determinants and environmental conditions determining the behavior
  3. Logic model of change: selecting methods of behavior change and translate to applications
  4. Program development: combine applications into a coherent program, pretest, and produce
  5. Implementation: anticipate on implementation of the program
  6. Evaluation: evaluate the program and optimize where necessary

Of these six steps, steps 2 and 3 will be used to illustrate how to use justifier when developing intervention using the Intervention Mapping protocol. There are two reasons for this.

First, these two steps will be the most familiar to psychologists involved in behavior change intervention development. The determinant studies conducted in step 2 have been part and parcel of health promotion and education efforts for decades, long before the term ‘behavior change science’ gained popularity. Similarly, studies into behavior change principles (called ‘methods for behavior change’ in Intervention Mapping, and called ‘behavior change techniques’ in the Behavior Change Wheel) have been conducted for decades within various subfields of psychology (see e.g. Leventhal, 1970).

Second, a tool has been developed that conveniently captures and makes explicit a number of important products of steps 2 and 3: the Acyclic Behavior Change Diagram (ABCD). The ABCD generates a visualisation of the full logic model of change, showing many of the structural and causal assumptions underlying an intervention. This diagram is generated on the basis of a matrix (the ABCD matrix), which has seven columns, each of which represents a series of decisions in the intervention development process. As such, justifying each of these decisions comprises a substantial proportion of the justification of the entire intervention development process.

Behavior Change Wheel

This introduction will be added later.

Example 1: Intervention Mapping (Acyclic Behavior Change Diagrams)

This first example follows parts of steps 2 and 3 of the Intervention Mapping protocol at the hand of the seven columns of the Acyclic Behavior Change Diagram matrix.

Justifying the selected target behavior

Before it is possible to analyse why target population members exhibit a behavior they exhibit, selecting such a target behavior is necessary. Behavior change interventions do, after all, need a target behavior.

To include the decision to select a target behavior, a fragment like this can be used:

Every justifier element must have a unique identifier (id), and in addition, can optionally have a type. Specifying a type for a decision will enable automatic processing when a framework is applied. Frameworks specify, for decisons of given types, how to organise them relative to each other (e.g. the order of the decisisons in a procedure), what acceptable values for the decisions are (if any), and allow some validation to check for those values.

In addition, to an id, all justifier elements can have a label and a description. A label is a human-readable short title for the element, and a description allows for more details. The date field allows specifying when the decision was taken.

In justifier, every decision has a justification. Each justification is based on one or more assertions, which are each based on one or more sources. A source can be an academic article, an unpublished report, the result of a consensus meeting with experts, the opinion of the planning group (an Intervention Mapping term), or even the opinion of one individual. The explicit definition of sources makes it possible to trace back the origins of assertions. An assertion is an assumption or statement of fact. This is loosely based on assertions as defined in nanopublications (see; in this sense, a source can be considered a very rough specification of an assertions provenance). Thus, a list of all assertions documented in an interventions justification shows what the intervention developers knew about, or believed to be true about, the world (and a list of the sources shows where that knowledge or those assumptions came from).

The justifications combine one or more assertions into coherent reasoning supporting a decision. A decision can have multiple justifications (but the entire justification can also be formulated within one justification element; so the number of justifications on which a decision is based is not necessarily a proxy for how well-supported a decision is).

Any source, assertion, and justification can be re-used; they have, after all, unique identifiers. In addition, these elements can be specified on their own, or within their parent elements. For example, the following constitutes a valid source definition:

This source can then be used in assertions elsewhere.

Justifying selected sub-behaviors

Once the target behavior is clear, Intervention Mapping prompts identification of all sub-behaviors that make up the target behavior (called ‘performance objectives’ in IM vocabulary). Sub-behaviors are distinguished by having different psychological determinants and/or environmental conditions. Not all sub-behaviors are selected for intervention. Resource constraints often necesitate selection.

To justify choosing or not choosing a sub-behavior, a fragment like the following can be used:

As can be seen here, there is no real difference between the justification and assertion; for such simple facts, there is not much reasoning required to tie it into a decision.

Justifying selected determinants

Ideally, for every performance objective, all determinants are mapped as comprehensively as possible (as are the enviromental conditions and the environmental agents who control those, but ABCDs deal only with behavior change within target population individuals). From this full overview of potentially relevant determinants, resource constraints will often necessitate selection of a subset of determinants to target in an intervention.

To justify choosing or not choosing a determinant for a sub-behavior, a fragment like the following can be used:

Justifying selected sub-determinants

Intervention messages cannot target behavioral determinants directly, because such determinants are defined as generic constructs. On the one hand this enables studying behavioral determinants over a variety of behaviors and populations, but on the other hand, it renders them insufficiently specific to verbalize or visualize. Therefore, interventions target the specific sub-determinants that underlie each determinant. In a way, tehrefore, subdeterminant selection is more important than determinant selection (although it’s very important to know to which determinant a sub-determinant belongs; this is required to select the behavior change principles).

To justify choosing a sub-determinant, a fragment like the following can be used:

Justifying selected behavior change principles

Once the relevant subdeterminants have been selected, the concrete intervention targets are known. It then becomes possible to think about which behavior change principles (BCPs) are most likely to be effective to change those subdeterminants. Lists of behavior change principles are available as methods of behavior change in the Intervention Mapping book (and the open access article by Kok et al., 2016), and some of the behavior change techniques may also contain effective elements (see for example Abraham & Michie, 2008). In addition, the psychological literature contains a wealth of theories and empirical evidence on behavior change principles that are not included in either list. For example, there’s a list being developed of self-determination theory-based behavior change principles (see

Justifying applications

Behavior change principles (BCPs) are theoretical principles that describe a procedure for successfully leveraging evolutionary learning processes. Because organisms’ ability to learn is very general, both ELPs and BCPs are formulated at a general level. Most BCPs can therefore take a variety of conrete forms, enabling applying the same BCPs in interventions that use brochures as are used in smartphone apps or school programmes. This enables applying BCPs in whichever form is optimal given the population, context, or intervention delivery scenario.

To justify an application, a fragment like the following can be used:

Justifying conditions for effectiveness

Because behavior change principles are defined at a higher level than the very fundamental evolutionary learning processes, their description often leaves many degrees of freedom. Yet, their final application must closely approximate the conditions under which the underlying evolutionary learning processes work. The parameters for this approximation are captured by a BCPs parameters for effectiveness. In addition to these parameters for effectiveness, applications have to meet conditions relating to the target population (e.g. what is acceptable to them), culture (e.g. what fits with the held belief systems), and context (e.g. what is possible in the situation where the intervention will be delivered). Together, all these conditions are called the conditions for effectiveness. Any application of one or more BCPs must meet the relevant conditions for effectiveness.

To justify which conditions for effectiveness exist and how they are satisfied, a fragment like the following can be used:

Deliberate omissions

There are many more choices to make during intervention development, but two are obviously omitted here and so deserve mentioning. Both capture those factors that contribute to behavior that are not part of the target population’s psychology: their environment. First, the environmental conditions themselves; and second, the environmental agent(s) under whose control those enviromental condition(s) are. These are not included in this vignette because this vignette is based on acyclic behavior change diagrams (ABCDs), which are a tool to work with behavior change efforts that directly target individuals; other tools exist for other aspects of intervention development.

Example 2: the Behavior Change Wheel

Justifying …

Justifying …

Justifying …

Epilogue: theory from practice

Some phases in the intervention development process, such as steps 2 and 3 from Intervention Mapping, are relatively comprehensively documented. Navigating through these steps is hard and requires combining competences from many disciplines, but quite tangible procedures have been developed to guide this process. However, other phases lack such comprehensive guidance. This often leaves novice intervention developers somewhat in the dark.

At the same time, experienced intervention developers often did develop implicit procedures they apply when working through these steps. Such procedures often represent valuable lessons for less experienced intervention developers, yet are rarely available in any codified manner. Instead, they are learned through experience, in the best case - which still results in many sub-optimally developed interventions along the way.

Application of justifier makes it possible to map the decisions that are taken and identify patterns. In addition, it makes it possible for the intervention developers themselves to identify the weak links in their intervention development process: for example, the points where they take their decisions with weaker justifications.

Because justifier is a very general-purpose justification standard, it does not require an a priori specified list of intervention development decisions. Frameworks can be applied to systematically process decisions and justifications, but without frameworks, justifier still allows intervention developers an easy way to document their decisions and justifications in a format that can later easily be procesessed.

This means that it is feasible to employ justifier even in processes that are entirely new. This means that process evaluations can be thorough even for aspects of a process that could not be specified a priori, and no important information is lost. Decisions and justifications can be automatically imported and categorized to facilitate efficient processing.


Crutzen, R., Peters, G.-J. Y., & Noijen, J. (2017) Using Confidence Interval-Based Estimation of Relevance to Select Social-Cognitive Determinants for Behavior Change Interventions. Frontiers in Public Health, 5, 165. doi:10.3389/fpubh.2017.00165

Kok, G., Gottlieb, N. H., Peters, G.-J. Y., Mullen, P. D., Parcel, G. S, Ruiter, R. A., Fernández, M. E., Markham, C, Bartholomew, L. K. (2016) A taxonomy of behaviour change methods: an Intervention Mapping approach. Health Psychology Review, 10, 297-312. doi:10.1080/17437199.2015.1077155

Leventhal, H. (1970) Findings and Theory in the Study of Fear Communications. Advances in Experimental Social Psychology, 5, 119-186. doi:10.1016/S0065-2601(08)60091-X