Wednesday, March 25, 2009

Argument Mapping and Analysis of Competing Hypotheses (AM vs ACH)


This article presents a comparative assessment of argument mapping (AM) and Analysis of Competing Hypotheses (ACH) as analytic diagramming techniques. While the paper focuses primarily on the differing techniques in diagramming a decision making pathway, the author considers both as "complementary analytical frameworks".

Comparing the Techniques
Both techniques involve analyzing a given proposition (hypotheses in ACH; conclusions in AM), evaluating the evidence (evidence in ACH; reasons and objections in AM), and diagramming a visual representation of the relationships (matrices in ACH; box-and-line diagrams in AM). In ACH, the letters C, I, and N represent positive (consistent), negative (inconsistent), or nuetral relationships, respectively. In AM, arrows indicate a relationship between the reasons supporting or opposing the conclusion; color indicates whether the evidence is a reason (green) or an objection (red) for the argument. When a piece of evidence is neither a reason nor an objection (neutral or irrelevant), the creator of the AM may choose either to eliminate it from the map or to make it a different color (typically gray).

Multiple Propositions
Due to the manner in which each of these methods handles multiple propositions, ACH gets the advantage over AM. ACH incorporates multiple propositions simply by adding another column in the matrix. However, adding any additional propositions to an AM may result in a cluttered diagram with crossed lines and complicated pathways. To resolve this issue, it may be more appropriate to duplicate pieces of evidence, or even create an additional map, making it less efficient.

Multi-tiered Evidence
The paper uses an example from Psychology of Intelligence Analysis to demonstrate a situation in which AM may be a more efficient method. The chosen proposition is "Iraq will not retaliate forUS bombing of its intelligence headquarters," and the piece of evidence in question is "Saddam [has made a] public statement of intent not to retaliate". Often, as cited in this example, an additional piece of evidence may be necessary to establish a piece of evidence. When using an ACH, the analyst may need to construct another matrix to validate evidence. The AM technique allows for the addition another level of evidence within the same map. The paper refers to the multi-tiered evidence as "granularity". Granularity allows evidence of differing levels of abstraction to be present on the same map; "the higher the level on map, the more general or abstract the reason or objection".


AM also allows the user to add assumptions or warrants alongside the pieces of evidence. Incorporating an assumption into an ACH would force the user either to add a justification with the conclusion in its cell in the matrix, or combine multiple pieces of evidence together.

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