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Build synthesis tree

Plan and visualize your literature review


 In this technique, you'll create a synthesis tree that organizes all the sources and how they relate to each other.

The grid of common points establishes agreements and disagreements between authors, while the synthesis tree helps you see the significance of these differences.  It's much easier to edit a synthesis tree than prose -- this will help you draft the bulk of your literature review quickly.

In the synthesis tree, you create an tree-like organization of different sources organized around issues, problems and solutions.  Different authors are grouped based on how they address these different aspects of the topic. 



Here is an example synthesis tree from Kaufer, Giesler & Neuwrith (1989, p. 165):


When you map the conversation in the literature, you need to relate points from different sources, which you can do concisely using a synthesis tree (or if you are describing it from your own perspective, an approach tree).

A synthesis tree characterizes splits, that is disagreement between authors.  There are several types of splits:

  • Major splits -- this is the point on which most of the authors disagree
  • Preliminary splits -- a preliminary split is one that occurs before the main split.  You might have to add a preliminary split to include additional authors.  For example, a preliminary split might involve an assumption that the majority do not share.  Or if the majority disagrees about a solution, the preliminary split may involve disagreements about the problem. 
  • Minor splits -- minor splits are added in order to further distinguish differences between authors

Splits usually occur around the milestones of the argument: 

  • seeing the issue -- these are questions about what problem cases need to be dealt with
  • defining the problem -- these are questions about the nature, sources, or best way to describe the problem that clearly articulates the tention in the problem case
  • choosing a solution -- these are questions about how best to address the problem

Synthesis/approach trees in design disciplines like learning sciences often look like this:

For example, "The community is concerned about problem case R, which is caused by X, Y, & Z, but the most important cause to focus on is Y.  Y has been insufficiently addressed by solutions A & B, but there is a promising approach C that is now possible / has been previously ignored / people disagree about.  To address Y, in this study we try C."

Of course, sometimes people will often argue with earlier parts of the argument, like we don’t even know the much about the problem at are, in that case the synthesis tree is more like:

For example: "We see some problem case R, but we know very little about what causes R.  To address this, we investigate the causes of R."

Other times, there is just some new kind of problem people haven’t looked at, which leads to a synthesis tree like:

For example: "Our community cares about learning, and we have explored problems Q, R, and S in context M, however, we know little about context N which is also important.  To address this, we will look at context N."

In design disciplines like LS though we are usually interested in design solutions because we want to promote learning.  The later synthesis trees are just first steps toward getting to a solution that promotes learning.





Before you start, you should already have a grid of common points among your sources as described in Creating an Argument Grid

This will help you create your synthesis tree much faster.


Step 1. Find the splits

Start by creating branches in the tree that represent the major splits, then add in preliminary splits if necessary, followed by as many minor splits as you need to characterize all the sources.

Step 2. Label the splits

Now, label the splits with the central questions to reflect the movement from problem to solution.  That is, each label should occur at either at:

  • issue
  • definition
  • solution

Step 3. Revise splits

Now revise the labels on the alternative branches so that they are most informative.

Make sure to avoid yes/no, should/shouldn't framings of the problem and to use more descriptive labels.  For example, don't use: "pro/con abortion" but "pro life/pro choice" because it tells you more about each author's position. 

Step 4. Characterize authors' positions at leaves

Insert a characterization of each author's position at the end of the branches.

When you put the author at the very bottom (leaves) of the tree, don't just put the authors name but give a shorthand statement of the author's position.

Step 5. Review for overall coherence

Now revise the tree for overall coherence by making sure that:

  • general questions should precede specific questions
  • the answer to one question should lead naturally to question following
  • the author's position should be logical result of questions and responses preceding it

If your tree doesn't pass any one of these tests then revise until it does.

Rookie Mistakes





Critique questions





This technique is from Kaufer, Geisler & Neuwirth (1989, ch. 7).

Kaufer, D.S., Geisler, C., Neuwirth, C.M.: Arguing from sources: exploring issues through reading and writing. Harcourt Brace Jovanovich, San Diego, CA (1989)