My intuition says that creativity is network-based and rational thought is hierarchy-based. Note that a hierarchical tree is simply one form of network or graph.
Also, there is no fundamental difference between graphs and matrices. This could explain why natural language researchers have not been so excited about latent semantic analysis (LSA), which is simply one way of representing a graph in a format that the computer can operate on naturally. This graph represents certain relationships in “meaning” between words.
Finally, an LSA/graph approach may or may not be more appropriate than a hierarchy/grammar approach, depending on the specific problem to be solved. Graphs are less constrained and therefore seem most powerful, though also potentially need a lot more computational resources. Also, human brains appear to be general networks, not constrained to hierarchies, but that may or may not be important to know.