In the 1950’s, George Miller wrote
a famous article about the limitations of working memory called “The Magical
Number Seven, Plus or Minus Two.” The title was Miller’s way of saying that the
number of bits of information we can handle in the brief span of working memory
is very limited — five to nine items at most.
The acquiring of academic skills,
including notably a big vocabulary, consists of building efficient mental
systems that enable us, despite our very limited working area, to perform feats
of analysis and synthesis.
A famous experiment conducted by Dutch
psychologist Adrian de Groot illustrated this universal bottleneck in human
processing skills. He noticed that chess grand masters have a remarkable skill
that we amateurs cannot emulate. They can glance for five seconds at a complex
mid-game chess position of 25 pieces, perform an intervening task of some sort,
and then reconstruct the entire chess position on a blank chessboard without
making any mistakes.
Performance on this task correlates
almost perfectly with one’s chess ranking. Grand masters make no mistakes,
masters a very few, and amateurs can get just five or six pieces right.
(Remember the magical number seven, plus or minus two.)
On a brilliant hunch, de Groot then
performed the same experiment with 25 chess pieces in positions that, instead
of being taken from an actual chess game, were placed just at random on the
board. Under these new conditions, the performance of the three different
groups — grand masters, masters, and novices — was exactly the same, each group
remembering just five or six pieces correctly.
The experiment suggests the skill
difference between a master reader who can easily reproduce the 16 letters of
“the cat is on the mat” and a beginning reader who has trouble reproducing the
same letters.
An easy-to-remember chess layout
If the
16 letters were “rtu kjs vb fw nqi pgf,” the expert would exhibit little skill
advantage over the novice; on average, neither will get more than a short
sequence of the letters right.
Practised readers, chess grandmasters,
and other experts do not possess any special mental equipment that novices
lack, and they do not perform any better than novices on similar yet unfamiliar
tasks. Nonetheless, experts are able to perform remarkable feats of memory with
real-world situations such as mid-game chess positions and actual sentences.
How do they manage?
The sentence “The cat is on the mat”
consists of six words that are easily remembered. Expert readers can easily
reproduce the 16 letters, not because the letters are individually remembered,
but because they are reconstructed from previous knowledge of written English.
What de Groot found, and subsequent
research has consistently confirmed, is that the difference in higher-order
skill between a novice and an expert lies not in mental muscles but in what de
Groot called “erudition,” a vast store of available, relevant,
previously-acquired knowledge.
Despite the narrow limitations of
working memory, the wealth of contents that can be manipulated by experts
through this previously-acquired erudition is immense.
If I already know a lot about
baseball, the term “sacrifice fly” can summarize a page or two of exposition.
Such shorthand representation is a chief time-saving technique of higher-order
skills.
The phrase “World War II” is short and
therefore easily remembered, but the content represented by the phrase cannot
be grasped by those who, however skillful in other ways, lack that relevant
knowledge.
I use these examples as a rapid way of
indicating why an academic skill like reading depends on learning much more
than the foundational ability to form sounds from symbols, turn the sounds into
words, and put the words together in sentences.
While such formal skills are
critically important, they are quite insufficient to comprehend a passage about
World War II in the absence of relevant background knowledge. The skill of
reading (and listening) depends on, among other things, a previous knowledge of
what most of the words in a text mean and refer to.
De Groot showed that being an expert
in chess does not improve one’s memory for randomized chess positions. Tracing
the implications of that discovery, psychologists have found that being a
critical thinker in chess is not likely to improve one’s skills in areas other
than chess, like mathematical problem-solving or the ability to think logically
about politics. This is one of the most solid findings in psychology, confirmed
and reconfirmed many times.
The reason can be traced back to the
bottleneck of working memory. The ability to solve any problem depends on
having a specifically relevant and available vocabulary and body of knowledge.
(Adapted with permission from “Not So Grand
a Strategy” in Education Next, Spring 2003. Dr. Hirsch is professor
emeritus of English at the University of Virginia)