Also known as Blocks and Barriers, it is useful in situations where different interest groups have different perceptions of the same problem.
- The group can contain up to twelve members. Each member brainstorms blocks and barriers which contribute to the persistence of the problem in hand. This is done privately and anonymously.
- The statements are collected and a special voting procedure is followed – anonymous, if necessary – whereby each member allocates ranks to each problem statement. This leads to clusters of problem for subsequent attention.
This technique is named after its creators Andre Delbecq and Andrew van de Ven. Together they also invented the Nominal Group Technique (NGT) decision making method.