Summary: The fifth in Stewart Mennin's Wicked Issues series of blogs, this time on the subject of Pattern Logic and the CDE Model: How to shift and influence Wicked Problems Description:

Two Common Patterns

We know the world through our perception and understanding of patterns.  We notice them all the time, although usually we are not conscious of it.  It just happens.  There are many different types of patterns:  design, art, sewing, music, dance, architecture, etc.  Some patterns are simple and predictable like measuring vital signs or one best answer multiple-choice question. Others are complicated, variable and more or less predictable, i.e., conducting a polio vaccination program for children at a local school.  Still other patterns are complex and unpredictable like chronic illness, social determinants of health, interprofessional collaboration and coherent institution-wide assessment programs (Glouberman and Zimmerman, 2002). For the purposes of the present blog, we focus on two types of patterns common to health professions education, practice and health care systems;  impact cause and effect and patterns and complex patterns in Wicked Problems.
Impact patterns are the result of linear cause and effect. Their logic is characterized by inputs directly linked to outputs and outcomes.  Impact patterns fit well with Newtonian laws of physics and Cartesian reductionism (Doll Jr, 1993), Table 1.

Table 1.  Comparison of Patterns due to Impact cause and effect logic and Pattern Logic, complex and Wicked Problems. 

The second type of pattern is complex.  Wicked Problems are complex patterns because they cannot be understood, controlled or solved with traditional linear cause and effect logic (Rittel and Webber, 1973).  Instead, complex patterns and Wicked Problems are best understood using Pattern Logic.  Pattern Logic provides you with the ability to see, understand and influence patterns that emerge in and across contexts in complex adaptive systems such as health care and medical education.

Pattern logic: (CDE) Containers, Differences, Exchanges

Pattern logic is based on and three interdependent features: similarities, differences and connections. Medical students and practitioners often find themselves in novel, uncertain and unpredictable situations. Faced with uncertainty, we intuitively look for patterns that inform our choices of behavior. Pattern Logic brings patterns to conscious mind and facilitates learning to work with them with more ease and confidence. The structure of Pattern Logic involves three features that are easy to understand (G. H. Eoyang, 2016).
  1. Boundaries define the space occupied by a complex pattern or Wicked Problem. What are the clusters of things that are similar? What belongs together? What are the groups, areas, and spaces that are set apart in some way from others?  Where are the walls that separate, the openings through which contents to pass in and out of the container? Both selectively permeable cell membranes and the idea of cells are examples of an open yet bounded container, one physical and the other conceptual.  In Pattern Logic, boundaries hold things together.  They function as containers (C) (Figure 1). Containers can be physical—like real walls. They can also be social, political, emotional, and informational like the concept of cells. Anything in the bounded space that divides the “same” from the “other” functions as a container in Pattern Logic.

    Containers are many and varied and can be massively entangled in any situation, especially wicked problems. One example of a way to shift boundaries in a wicked problem in a medical school or practice is political know how, i.e., the ability to create, respect, or cross boundaries and the wisdom to choose when to do which (G.H. Eoyang and Holladay, 2013; G. H. Eoyang, 2016). Being conscious of and naming containers provides the capacity to thrive in any challenge, any place or time.

  2. Differences (D) are what matters to us, what is important. Human systems are capable of embracing an enormous number of differences; the vast majority of which are subliminal and go unnoticed. For example, in medical education and clinical settings there are subtle differences among people, cultures, languages, settings, groups, environments, positions, movement, color, light, etc. We each have different expectations, relationships, values, history, rules and ways of living. A human system is a collection of different people both inside and outside of the container being observed.  The importance of a curriculum committee meeting or a group practice meeting, for example, depends on the similarities and differences among those who are in attendance (in the container); the number of issues on the agenda and the time available to discuss and decide them; the history of what has happened before, etc. The committee or group is also influenced by what is happening outside of the meeting in the school, hospital, clinic and community.

    Differences inside the container create tension expressed as potential energy for change. “The significance of differences is based on context, and because contexts change all the time, so do the differences that make a difference. Pattern Logic helps you pay attention to see and respond when significant differences shift” (G. H. Eoyang, 2016).  
  1. Connections.  We are social beings that live through connections.  Connections can be both relationships and ideas.  They are a form of exchange of energy, information and substances. In Pattern Logic, connections are called exchanges (E).  The release of tension through exchange determines when and how things move and change. Change can be fast and predictable as when connections are tight, as when people hold strong beliefs, value close relationships, or have a sense of permanent place. Change can be slow and unpredictable as when connections are weak, transient and emotional.
The sooner you see and understand connections, the more prepared you are to engage consciously and with intention. That is why exchanges are such a significant aspect of the adaptive capacity that comes from Pattern Logic. Like containers and differences, exchanges are many and constantly changing. Only Pattern Logic can help you recognize and engage wisely in connections that are important for you and your group.  

Figure 1.  The CDE Model.  The purple semicircles are the boundaries of the containers (C).  The colored objects represent differences (D). The dashed lines represent connections and exchanges (E) among the contents of the containers. Understanding the relationship among the CDE provides an explanation for complex patterns and opens the possibilities of influencing them. (See blogs 1-4 (


The CDE Model: Influencing Patterns in Wicked Problems

Taken together, the CDE are the logic of a complex adaptive system.  It is how we can understand and influenced the patterns in Wicked Problems.  In the curriculum committee and group example, the container (C) is meeting.  Differences are the professional identities of members of the group.  What are some similarities you can think of among the people inside the container? To what extent might any similarities, differences and connections in these groups accessible to you?  What might be the effect if one new member joins or leaves the group? This small change of one person alters the tensions in the meeting. How are the connections between people in the container?  Are they tight, strong, fast and few? Are they loose, weak, slow and numerous?  In any given Wicked Problem one or more of the CDE features are accessible to you.  Most often, what is accessible to you is your own perspective, understanding and choice of action.  You can’t predict what will happen in the group. So, the best strategy is to try something and see what happens.  Adaptive Action is a mechanism to see understand and influence complex patterns and Wicked Problems (G. H. Eoyang, 2011; G.H. Eoyang and Holladay, 2013). 
Adaptive Action (Figure 2) consists of three simple questions: What? So What? and Now What?  What are the similarities, difference and connections in your Wicked Problem?  So What is important to you? To Others? So What are your options?  Now What will you do to shift the pattern?

Figure 2.  The three questions of Adaptive Action.
So, the next time you enter an unfamiliar space or face an intractable challenge, step beyond your intuition or traditional logics and embrace the emergent power of Pattern Logic. You will see, understand, and influence, even when you cannot possibly predict or control.


For a deeper dive, get your hands on a copy of Adaptive Action by Eoyang and Holladay, 2013; read the first four blogs in this free series ; register for the online AMEE ESME Essential Skills in Action Course, learn more plus get individual help with your Wicked Problem


Doll Jr, W. E. (1993) A post-modern perspective on curriculum. New York: Teachers College press.

Eoyang, G. H. (2011) 'Complexity and the Dynamics of Organization Change ', in Allen, P., Maguire, S. and McKelvey, B. (eds.) SAGE Handbook of Complexity and Management London: SAGE,  pp. 319-334.

Eoyang, G. H. (2016) Pattern Logic. Available at: (Accessed: July 22, 2018).

Eoyang, G. H. and Holladay, R. (2013) Adaptive Action: Leveraging uncertainty in your organization. Stanford, California: Stanford University press.

Glouberman, S. and Zimmerman, B. (2002) Complicated and complex systems: what would successful reform of Medicare look like? Available at:

Mennin, S. (2007) 'Small-group problem-based learning as a complex adaptive system', Teaching and Teacher Education, 23, pp. 303-313,

Miller, G. E. (1990) 'The assessment of clinical skills/competence/performance', Academic medicine, 65(7), pp. S63-S67,
Rittel, H. W. J. and Webber, M. M. (1973) 'Dilemmas in a general theory of planning', Policy Sciences, 4(2), pp. 155-169.