MadSci Network: Neuroscience

Re: Is Miller's study on short term memory of the brain still valid?

Date: Tue Nov 16 20:37:25 1999
Posted By: Michael Freed, Research Scientist, Aerospace Human Factors, NASA Ames Research Center
Area of science: Neuroscience
ID: 935853703.Ns

The Miller result is still interesting enough to get cited, but his 
explanation for it long since been superceded by other findings.  The 
literature is pretty substantial.  I'd recommend Baddley's 1990 book called 
Human Memory for a good overview.  But for now, here a few things you might 
find interesting.

1.  The ability to recall about 7 items is now thought to arise from the 
performance of 2 memory systems -- a short term "working memory" and some 
kind of long term memory (LTM).  The idea is that you start encoding the 
first items in LTM, but can't keep up, so only the first few items are 
available.  You also can remember the last few (most recent) items of a 
list due to the "recency effect" -- working memory tends to store recent 
items and throw away older ones.  For longer lists, people tend to forget 
the middle items which are too late to get encoded in LTM but too old to 
avoid getting overrun in working memory.

2.  Working memory is thought to be composed of several different stores -- 
one for each sense.  A verbally presented list will get stored in the 
"phonological loop."  This seems to be something like a 2-second long strip 
of audio tape that gets continually overwritten.  It turns out that the 
"digit-span" -- number of digits can be recalled -- varies for speakers of 
different languages.  Chinese speakers can do a little better than 7 +-2 
because they can fit more digits in their 2 second loop.  Welsh speakers do 
 the worst because there names for digits are longer words.

3.  The story gets a lot more complicated when looked at in detail.  What 
one remembers has to do with how the info is processed.  For example, if I 
give you a list to remember that consists of all digits except for one 
totally different item -- say the name of a fruit -- you will have no 
trouble remembering the fruit even if it was presented in the middle of the 
list.  The idea is that you processed the meaning of the word and encoded 
it separately in memory.  There are numerous findings of this sort.

Regarding your question about memory development, I'm afraid I don't know a 

Good luck to you!

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