Miller's number

from Wikipedia, the free encyclopedia

The Miller's number describes the fact described by George A. Miller in 1956 that a person can only hold 7 ± 2 information units ( chunks ) in short-term memory at the same time . The size of the short-term memory is genetically determined and cannot be increased by training. Miller's related article, The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information, is one of the most cited articles in psychology .

The seven phenomenon

Even John Locke discovered the so-called over 300 years ago seven phenomenon when he examined the uptake of an adult. He found that test persons who see a large number of objects for a brief moment and then have to remember them have a hit rate of almost 100 percent with up to 7 objects. If there are more than 7 items, the quota drops suddenly. The human being is able to repeat up to 7 chunks a short time later after only one brief sighting , but only very rarely more. Average capacity is 6 to 7 chunks. A short-term memory of 8 chunks would already be above average.

Effects in practice

Methods for dealing with complex systems (cf. Fredmund Malik , requirements management , software engineering ) are always aimed at breaking them down into manageable units. The limit of manageability is often reached when the number of system elements reaches 7.

This explains various effects and recommendations:

  • Hierarchies become ineffective if more than 7 employees at one level have a direct manager.
  • If more than 7 goals are pursued at the same time, the overview is lost.
  • Meetings with more than 7 participants become less efficient.
  • Project groups without a hierarchical structure lose a lot of efficiency with 7 or more people.
  • An outline level in documents should not have more than 7 sub-headings.
  • A website should have a maximum of 7 navigation points.
  • In programming , a method should not have more than 7 parameters .
  • In object-oriented development , a class should not have more attributes than can fit in the developer's short-term memory. Class hierarchy levels should also be restricted.
  • In Scrum , a process model of agile software development , 7 ± 2 was given as the ideal size for a team. However, due to greater flexibility, this was adjusted to 6 ± 3.
  • A group is only manageable for the individual member if it consists of a maximum of 7 other people:
    • A troop is the smallest form of military structure and consists of a maximum of 8 men.
    • A contubernium , the smallest organizational unit in the ancient Roman army , consisted of 8 men.

Although Miller's number is not entirely undisputed and recent studies suggest that it is already out of date today, it provides a good orientation and is disciplined to limit itself to the essentials.

criticism

The focus on the number 7 as a phenomenon is already doubtful due to the original experiments by Miller, since in these the full recognition was with 7 numbers, 6 letters or 5 words. The amount of recognized information was therefore dependent on the type and, above all, the length of the chunks. Baddeley later suggested that working memory is not limited by number, but by length of time. All chunks that can be spoken in two seconds can be fully processed. Further research by Baddeley showed that chunks that belong together are easier to remember. In this way, sentences with 15 words or more can be reproduced exactly in the experiment. On the other hand, it can be seen that a lower limit is already occupied by simultaneous recording of 4 to 5 chunks. Baddeley's model is presented in more detail in the article “ Baddeley's Working Memory Model”.

Research from the University of Missouri, repeating the experiment with symbols, found that on average, humans can only retain 3 to 4 information chunks in working memory.

See also

literature

  • George A. Miller: The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information . The Psychological Review, No. 63 , 1956, pp. 81-97 , doi : 10.1037 / h0043158 ( musanim.com ).

Individual evidence

  1. DW. Gorenflo, J. McConnell: The Most Frequently Cited Journal Articles and Authors in Introductory Psychology Textbooks. In: Teaching of Psychology. 18, 1991, pp. 8-12, doi : 10.1207 / s15328023top1801_2 .
  2. ^ W. Kintsch, J. Cacioppo: Introduction to the 100th anniversary issue of the Psychological Review. In: Psychological Review. 101, 1994, pp. 195-199, doi : 10.1037 / 0033-295X.101.2.195 .
  3. E. Garfied: Essays of an Information Scientist . (PDF; 696 kB) 8, 1985, pp. 187-196; Current Contents, May 20, # 20, pp. 3-12.
  4. ^ Z. Giora: The Magical Number Seven . In: D. Robert (Ed.): Occident and Orient. Budapest 1988, ISBN 90-04-08169-0 , p. 175 ff.
  5. a b c d e Miller's number. In: Christian Glaser, Risk in Management, Springer Fachmedien Wiesbaden. 2019, accessed October 22, 2019 .
  6. Steve McConnell: Code Complete. A Practical Handbook of Software Construction . 2nd Edition. Microsoft Press, 2004, ISBN 978-0-7356-1967-8 , Chapter 7.5: How to Use Routine Parameters - Limit the number of a routine's parameters to about seven , p. 202 (English).
  7. Arthur J. Riel: Object-Oriented Design Heuristics . Pearson Education, 1996, ISBN 978-0-321-77496-5 , Chapter 4.6: The Containment Relationship, Heuristic , Chapter 4.7: Classes should not contain more objects than a developer can fit in his or her short-term memory , Chapter 5.4 : The Width and Depth of Inheritance Hierarchies, Heuristic , Chapter 5.5: In practice, inheritance hierarchies should be no deeper than an average person can keep in his or her short-term memory .
  8. Ken Schwaber , Mike Beedle: Agile Software Development with Scrum . Prentice Hall, Upper Saddle River 2001, ISBN 978-0-13-067634-4 , pp. 36 (English).
  9. Ken Schwaber and Jeff Sutherland : The Scrum Guide. P. 6.
  10. ^ MU Psychologists Demonstrate Simplicity of Working Memory University of Missouri, News Bureau, April 23, 2008
  11. JN Rouder et al. An assessment of fixed-capacity models of visual working memory. In: Proc Natl Acad Sci US A. April 22, 2008, Volume 105, 16, pp. 5975–5979, doi : 10.1073 / pnas.0711295105 , PMC 2329704 (free full text)