Dynamic Tagging Theory

Summary
Short-term memory is explained by the Dynamic Tagging Theory. When you are exposed to a piece of information, your brain activates or “tags” long-term memories related to it until you have the information fully in mind. When you cease being exposed to the information, the tagging begins to lessen. If you have to remember the information, your brain “retags” long-term memories until you either have the information fully in mind again or fail to recall. Your chance of failure increases as the tagging decays. The time it takes to retag has to do with the amount of long-term memories related to the information in question, so a nonsense word is easier to recall than a familiar term.
Neurological Mechanism
The brain functions which probably permit tagging/retagging and tagging decay are exocytosis and endocytosis, which are the depletion and restoration of neurotransmitter in the synapses, respectively. We see this parallel because exocytosis occurs at a linear rate with respect to time and endocytosis at a logarithmic rate. That is exactly how tagging and tagging decay occur as well, the former linear with respect to time and the latter logarithmic. See figures 1 and 2 ([http://www.avabiz.com/avabiz/dhp.nsf/0/8df482a3aac6acdc852576e1004c663d/$FILE/The%20TaggingRetagging%20interpretation%20of%20short%20term%20memory.pdf 1]).
The Impact of Presentation Rate
Referring to the figures above, the slope of the tagging decay curve changes depending on the presentation rate for each piece of information. The presentation rate is the amount of items you are exposed to in a given time, say 1 item/second. The faster the rate, the faster your brain can tag long-term memories related to it but also the faster the tagging will then decay. The opposite occurs the slower the presentation rate. See figures 3 and 4 ([http://www.avabiz.com/avabiz/dhp.nsf/0/8df482a3aac6acdc852576e1004c663d/$FILE/ShortTermMemoryIsExocytosis.pdf 3]).
Explaining the Bowing Effect
There is an interesting phenomenon in short-term memory called the bowing effect. See figure 5 ([http://www.avabiz.com/avabiz/dhp.nsf/0/8df482a3aac6acdc852576e1004c663d/$FILE/PresentationRate.pdf 2]). When you read a list of information, you are likely to remember the first and last items better than the items in the middle. It makes sense that the last items, being the most recently observed, are easy to remember, but why the first items? This has to do with presentation rate. The first items in a list are being observed at a slower presentation rate than the items in the middle of the list because the first items have less competition from previously-mentioned items that demand the brain’s attention.

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