Spreading activation is a model for linguistic information retrieval within the human brain. The basic idea is that memory is a network of interconnected concepts. A particular concept is linked to related concepts by bonds. The ease with which related information is retrieved is dependant on the closeness/strength of the bond between two concepts.

In the above example the concept of "fish" has many related concepts, "chips" as in "fish and chips", "sea", "cat", "scales" and, of course, many others. The ease with which each of these related concepts is retrieved is dependant on how strong the bond is in your brain between the two concepts. For me, chips wins hands down, somewhat reflecting an obsession with food, for you it is probably something quite different. The bonds are not static but dynamically change with use. The more frequently a link is accessed the stronger it becomes. This usually reflects the importance of that link. Things that are extremely important occupy much of our thinking and we traverse this link many times as we are mulling over aspects of the particular issue or event.

Of recent times this concept has been embraced by the business community with the development of mind mapping techniques. These involve the representation on paper of networks that have a similar structure to the theoretical structures discussed above. Naturally this was rapidly followed by supporting software. Now everything from PCs, to PDAs to iPods have mind mapping software available.

The big question is whether external representations of this conceptual model of memory are effective. Many people swear by it and find it a valuable tool but little research has been done in this area. The big problem, or possibly advantage, of this sort of software is that we record what we think should be important to us not what actually is. This may be an advantage simply because the mind does very well by itself at handling the things that are really important to us. The software can be used for the things that our bosses think should be important to us.