From http://blogs.scientificamerican.com/beautiful-minds/the-controlled-chaos-of-creativity/

Fifty years ago, Sarnoff Mednick [] 

argued that creative people have flat associative hierarchies: they are better able to access distant, remote associations. For example, when given the concept "table", Mednick predicted that creative people would be more likely to retrieve more remote associations such as "leg" or "food". In contrast, Mednick argued that less creative thinkers have a steep associative hierarchy, in which words with a higher associative strength (e.g., chair) would be more likely to enter their minds:

Based on his theory, Mednick developed the Remote Associates Test (RAT). The RAT test presents you with three seemingly unrelated words (e.g., "fish-mine-rush") and you have to find a fourth word (e.g., "gold") that ties the other three words together.

While the RAT has been criticized as being more related to IQ and working memory than creative cognition, recent research on a number of fronts suggests that Mednick's theory is sound.*

Network Science

One exciting area of research is the application of computational network tools to examine the semantic memory network of creative people. Based on mathematicalgraph theory, a semantic network is comprised of "nodes" (concepts or words) and "links" that indicate the distance between them. Researchers are starting to use the tools of network science to elucidate various aspects of the creative process.

In Melissa Schilling's network model of cognitive insight, insight can be viewed as the emergence of clarity among a tangled web of thoughts and ideas. According to Schilling, cognitive insight occurs when an atypical association is made, resulting in a shortcut in a person's network of semantic representations. Insight affects the organization of the entire network, causing a decrease in path length, a new perspective on the entire network, and a cascade of other connections to come online.

Network science methodologies have also been used to compare the writings of prominent poets (e.g., Dylan Thomas) with prominent writers (e.g., F. Scott Fitzergerald). Sarjoun Doumit and colleagues found that poems show a "flatter" associative hierarchy than prose. According to Mednick's theory, this means that poems are more creative than prose, and involve the combination of more distant associations.