There are limits to the amount of information the mind can effectively process, and in the last few decades, research has demonstrated that beyond those limits, additonal information causes the quality of the decision to decline.
The mind can generate information at about twenty symbols per second, the top speed of typists and piano players, but can only receive at about sixteen symbols per second, the best rate of readers and listeners.1 Training can achieve slight improvements, but the constraint on information processing speed is biological.
There is also a limit on the number of alternatives the mind can consider at the same time. In his well-known essay "The Magical Number Seven Plus or Minus Two,"2 George A. Miller observed that while people can easily bear five or six choices in mind, they experience a marked reduction in processing ability when the number goes beyond seven. Individuals pick five or six radio or television stations they turn to regularly, even when there are many more on the dial. Executives generally manage five or six subordinates well, but not more than that3. Computer systems that present a menu of up to seven choices are easy to use, but those that go beyond that limit seem to be much more difficult. Together, these experiences hint at another biological limitation that, like processing speed, is difficult to overcome.
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