>This is interesting. How would it explain the large variance across people in
>performance on memory tasks - lists of random numbers, for instance. Is buffer
>size variable, or do some people pay more attention to each number. (whatever
>that would mean.)
My interpretation is that for visual tasks (I have no idea what happens when you learn a list of words) that the more items you attend to the worse the signal for each *individual* item. It just turns out that the trade-off between holding more items and increasing noise balances out and the effective capacity remains constant.
This limit does appear to be attentional and not memory related. So long as local motion cues are masked this capacity limit is present. So changes can be made to an item in a scene without someone noticing so long as there were visual transients elsewhere attracting attention. Likewise visual tracking tasks strongly suggest we can only track 4 items.
Ron Rensink (one of the key researchers in this area) told me the story of the Great Mephisto (?) from the 19th C who was able to produce a goat out of thin air. Mephisto would have a helper who came on before him and worked the audience up saying Mephisto was delayed, some emergency had come up etc. Suddenly the great magician appears off the side waving a huge red banner and shouting out to the audience as he strides out to the middle of the stage. As he reaches the center of the stage he casts the banner aside and suddenly in its place seemingly out of thin air is a goat. Alas our little brains just aren't able to process everything at once and so never noticed that the goat was under his arm the whole time.
Editor: PSYCHE: An International Journal of Research on Consciousness Board Member: The Association for the Scientific Study of Consciousness http://psyche.cs.monash.edu.au/ http://www.assc.caltech.edu/