Tuesday, November 22, 2005

On Memory - some questions and answers (by Owen)

"Human memory is designed to anticipate the future, not to recapitulate the past"

This posting follows the questions/comments posed to me by a friend. My answers/explanations follow.

what is the cognitive model of memory? Clearly the "human memory
is computer memory" metaphor is inadequate.

computer memory, like "library" memory etc. are inadequate models of memory because the presuppose a function for which there is no structure in the human brain. we have no memory chips, no shelves to store records of things to be retrieved later.

the replacement model is the "constructionist" model, that works as follows:

1. The human brain changes in response to experience by reinforcing neural connections related to the content of the experience. Concepts that are linked through experience become linked in the cognitive system. Example: cursing god's name and then getting in a car crash tends to make people cautious about insulting the Big Daddy again...

2. This structural change is Learning (conditionning that associates concepts with each other).

3. Learning about the relationships between things is the basis of the imaginative experience we call "memory". What we are really doing when we "remember" is building a plausible scenario in our imaginations based on our current knowledge. That is, remembering something is not accessing its record, stored somewhere in the brain and waiting for retrieval, but rather it is accessing current knowledge about relationships between things and creating an imaginary scenario that may be more or less vivid...

4. If connections are not actively reinforced (through experience or imagination) then they slowly fade over time. This is why "memory" is greater for recent events.

5. Repetitive events either reinforce the connections (slowly fading as usual between happenings) or cause more robust connections (i'm unclear on this so far).

6. Intense experiences (near death by bus) cause much stronger connections to be 'forged' between concepts in the brain, therefore creating a more permanent association. It may or may not be permanent, but it is clearly stronger and longer lasting.

In the textbook Cognitive Psychology, the overwhelming superiority of the constructionist model over the "record-keeping" model is laid out. Guenther (author of the chapter on models for memory) summarizes dozens of experiments designed to highlight the influence of changes in knowledge on experienced memories. The evidence is clear: new knowledge alters how we construct memories of past experiences.

The reason I ask is that I've noticed that people who get things done
have a very good memory for certain items:
-what they have asked others to do
-what others have asked them to do
-details about other people's lives that are of importance to them (i.e.
an interest in skiing or a sick child)

Experiments summarized in the book reveal that, confirming your observation, our memories are better for some things than others. They also reveal that the things we remember better have, surprise surprise, to do with things for which our knowledge is greater. This makes no sense from a record-keeping theory, but obviously follows from the constructionist model. The famous memory superheroes of the last century - people with "photographic" memories etc. turn out not to have photographic memories at all. In fact, even those with incredible memory for visual detail (eidetic imagers) report that it fades over time...

"Eidetic imagers report that, after viewing a picture, they see an image of the picture localized in front of them and that the visual details disappear part by part. While they remember many more visual details of a picture than would the ordinary person, often the accuracy of their reports is far from perfect".

Furthermore, the great rememberers (stage performers etc.) report that they use mnemonic techniques related to the realms of learning at which they excel. They associate new information with information that they already have a good grasp of.

The following is almost word for word from the book:

S. V. Shereshevksii was a famous memory show off who could remember lists of arbitrary and randomly presented words, 15 years later! He reported that he formed vivid and detailed images of every stimulus he was asked to remember and often associated the images iwth images of familiear locations, like Gorky Street in Moscow. He would later retrieve the words from memory by taking a mental "walk," noticing the images associated with the landmarks. This mnemonic technique is called the method of loci, and can be used effectively by anyone trying to memorize a list of stimuli. Techniques like the this improve memory because they make the information more distinctive, and because they associate the distinctive images with well learned knowledge/imagery.

Furthermore, making sense/meaning of the stimuli is critical. Chess masters are much better at remembering the locations of pieces on a chess board than the average college student - but only if the pieces are in positions that have followed the rules of chess. If they are in an arrangement that couldn't happen, that makes no "sense" then their memory for chess piece locations is no better than anyone else!

So, I'm interested in finding out how to build my memory in these areas.
There are numerous folk theories of memory and how to improve it.
Yet, the strange thing is I had a great memory in school for learning
all sorts of math, science and engineering mumbo-jumbo -- how is it that
my memory works far better for somethings than others?

So, as I said above the accuracy of your memory-reconstructions will naturally be better for things that:

a) you have greater knowledge/understanding
/interest in.
b) you are able to make distinctive by making it vivid in your imagination (picturing the sick child, the caring parent, the relatives, the drama etc.)
c) you use mnemonic techniques to relate new knowledge to established knowledge (in whatever ways your understranding/leaning system is strong).

Guenther recommends:

- Look for themes and patterns that organize the material you are trying to learn (so that you'll reconstruct it better later).
- Relate the material to things you already know (things that are vividly known for you, images, places, people, laws of physics).
- Do the learning in a way that mimics the conditions in which you will need to remember it (if it is essays you'll have to write about it, practise by writing essays).

Recommended book: Searching for Memory by Schacter (1996).

By the way, it is thrilling reading, this stuff. It has radically changed the way I think about my own life experience and memory reconstructions, but also helps me incorporate things people report to me much more sensibly...


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