Activated Memory

Activated Memory

We now have two useful facts.  One is that melodic contour is an active construction in the mind of a perceiving animal.  Take away the animal and all you have is variations in air pressure.  The second fact is that this construction process has a constraint.  It has to be fed notes sufficiently fast in order for them to be glued together as a melodic contour.  This is not a constraint that applies to music alone.  There is a global aspect of memory that seems to be bound up in a 2 second time scale.  To get a feeling for what is going on here we are going to need a couple of facts about basic memory phenomena.

Memory has not been studied systematically for very long.  Although people have known they have memories for at least several thousand years, the first recorded memory experiment was conducted around 1890 by a German psychologist named Ebbinghaus.  Nevertheless, people know a lot about memory because they can observe their own memory functions.  Knowing about your own memory is something that starts occurring around the age of 10.  Much of what I will discuss here you will already know but maybe not quite in the way that I will say it.

The first and most important distinction in memory content is between declarative and procedural knowledge.  Declarative knowledge consists principally of facts and states of affairs.  For example you know that 1+1=2.  That is in your memory.  You don’t have to refer to your fingers to verify it.  When you first learned about counting you probably also had clear memories of what else you were doing that day, who taught you, and so on.  All the personal issues surrounding 1+1=2 eventually get lost as we experience counting in a myriad of circumstances. Eventually all that is retrievable is the fact itself.  Fact knowledge and personal autobiography compromise the greater part of awareness, but it is dwarfed in both scope and content by procedural knowledge. All of our motor skills are procedural.  Knowing how to walk, how to put the spoon in the mouth, how to ride a bicycle, and so on are all procedural.

Procedural knowledge is organized into schemas, patterns of action.  These patterns begin with conscious awareness but eventually fade into the background as they become automatic.  When you are learning to play an instrument all of these issues are quite obvious.  For example, my trumpet teacher is quite keen on teaching me licks.  For a long time I could not understand why because it seemed like an awful lot to learn and fairly useless besides.  One of the first things I learned was that it is possible to play licks that I could not remember.  This state of affairs can arise because there are procedural forms of memory that are unconscious as well as declarative forms that are in awareness.  If I can consciously remember the first note, the rest of the notes in the lick often follow automatically.  This is because the lick, as a motor memory trace, becomes activated by the action of a valve press.  Often I find myself listening to the lick wondering how it comes out of me.  Experienced musicians have enormous amounts of procedural knowledge in their fingers that awaits activation.  They get this knowledge through practice.  Practice turns declarative knowledge of the notes into unconscious motor patterns.

There is one large difference between procedural and declarative knowledge.  Procedural knowledge is organized at a very primitive level and does not generalize easily.  Each lick or piece of music has to be practiced before it is in your fingers.  Nothing comes for free.  This is not true of declarative knowledge which is highly organized and consequently highly flexible and capable of rapid generalization.  The memory system that accesses declarative knowledge is known as semantic memory.  Semantic memory is organized similarly to the world wide web. All of our concepts live in a highly abstract network where the links are derived through association.  The process of association is what guides thought and gives us the experience of stream of consciousness.

Thought is pushed along the semantic network through a process that psychologists refer to as activation.  The stream is diverted depending on which branches are active at any given moment.  A simple example illustrates how thought is channeled.  Consider the sentence “He dug with a spade”.  The word “spade” is actually fairly ambiguous but when you read that sentence hopefully you were thinking about shovels.  Hopefully you were not thinking about cards.  The word “spade” is associated with knowledge about cards as well as knowledge about digging and when you come across the action phrase “He dug…” it is the digging knowledge that gets activated.

Memory activation is the way that animals like us gain access to our knowledge.  And this is as true of the procedures we  have automatized as the ideas that form the stream of thought.  There are enormous reservoirs of information that lies dormant in permanent memory stores.  At any moment we are using what is active.  I am interested in the time course of memory activation and the theory that I am developing considers music and thought to be essentially governed by the same kind of activation process.  The evidence that memory activation has universal properties comes from experiments like the one described in the next section.  In the following experiment I will show how the duration of activation can be measured in semantic memory and we will see that it is pretty close to the 2 seconds that limits musical coherence.

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