George Miller [Magical Number 7 +/-2] Part 4

From: Elizabeth Cole (ejc297@soton.ac.uk)
Date: Mon Mar 02 1998 - 11:47:16 GMT


Hi, everyone! I'll try and explain (if only in a kind of
muddled, I'm not too sure what's going on, kind of way) what
Miller was talking about in my part of the paper.
 
Part Four: Subitizing
 
Miller starts off by talking about an experiment by
Kaufmann, Lord, Reese and Volkmann, in which a number of
dots, from one to over 200, were flashed on a screen for only
one fifth of a second. The participants' job was to say how
many dots they had seen on the screen. The results of this
showed that for patterns containing 5 or 6 dots the
participants were ALWAYS correct. The name given to this was
the ability to "subitize" and was how the participants could
recognise virtually without fault patterns containing up to
SEVEN dots. However, as above seven the participants couldn't
recognise immediatly the number of dots, they had to
"estimate".
 
Miller then questions if this is the same process as when
"unidimensional judgements" are limited to seven catagories.
However, he concludes that there is a difference, as there
are several ways of processing the number of something (for
example the number of dots) "there are about 20 or 30
distinguishable catagories of numerousness". Therefore there
is a difference in the amount of information recieved from
one-dimensional and two-dimensional displays.
 
Miller then goes on to question if in a two dimensional
display, the relevent dimensions of numerousness are area and
density (which obviously wouldn't both be in a unidimensional
display). Therefore this would then lead to a
difference, depending on the dimension of the display, to how
information about the number of something is processed.
However, the number of items also has a bearing on how the
information is processed. Miller adds
 
 "When the subject can subitize, area and density may not
be the significant variables, but when the subject must
estimate perhaps they are significant"
 
Therefore, at least in the case of a two-dimensional pattern
of dots, there is a difference between the way in which
groups of below seven items are processed to estimating the
number of items if it is greater than seven. This is due to
other factors, such as the area and density of the display,
which affects the number of items guessed by the participant.
 
I hope I haven't confused you too much (although I think I'm
still a bit confused by it - but I tried my best!!).
 
Bye Liz
 
----------------------
Elizabeth Cole
ejc297@soton.ac.uk
 



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