Theory of the Week
- March 3, 2002
- Gaia Hyptothosis
Named after Gaea (gaa in Greek), the goddess Mother Earth. The theory that the Earth is a living organism with a self-regulating
mechanism that is yet undefined. All animals, plants and human activities are believed to contribute to the system, which has checks and
balances to ensure the continuance of life. The stability of atmospheric components over many eons is cited as evidence for this
controversial theory.
J Lovelock, The Ages of Gaia: A Biography of Our Living Earth (Oxford, 1988)
- February 19, 2002
- Pseudo Forgetting
The process whereby we think we know something (such as a telephone number), attempt to recall it and when we fail, conclude we have
forgotten it. The fact is we may never have stored the material or it may have been incorrectly stored. Either way the information cannot be
considered forgotten.
E F Loftus and G R Loftus, 'On the Permanence of Stored Information in the Human Brain', American Psychologist, vol. XXV
(1980), 409-20
- February 10, 2002
- Chicken
An application of game theory where political conflicts arise which are analogous to the game of chicken
in which two contestants will, for instance,
drive towards each other in motor cars. If both hold their course, both will crash. The one who saves herself, and so her opponent, is the
"chicken." As in other "games," the action of each participant is seen to be dependent in part on their estimate of the likely behavior of the
other. The Cuban missile crisis of 1962 is often described in these terms.
Robert Abrams, Foundation of Political Analysis (New York, 1979)
- February 1, 2002
- Brook's Law
"Adding manpower to a late software project makes it later" -- a result of the fact that the expected advantage
from splitting development work among N programmers is O(N) (that is, proportional to N), but the
complexity and communications cost associated with coordinating and then merging their work is O(N^2)
(that is, proportional to the square of N). The quote is from Fred
Brooks, a manager of IBM's OS/360 project and author of "The Mythical
Man-Month", an excellent early book on software engineering. The myth in question has been most tersely
expressed as "Programmer time is fungible" and Brooks established conclusively that it is not.
Eric S. Raymond (compiler), New
Hacker's Dictionary (The MIT Press, Cambridge, M.A., 1996)
- January 21, 2002
- Jakob's Law of the Internet User Experience
Users spend most of their time on other sites. This means that users prefer your site to work the same way as all the other sites they already know.
Homepage Usability: 50 Websites Deconstructed, by Jakob Nielsen and Marie Tahir
- December 30, 2001
- False Consensus Effect
The general tendency to overestimate one's similarity to others on attitudes, behaviors, and personality traits.
Unlike their unskilled counterparts, the most able subjects are likely to underestimate their own competence. Researchers attribute
this to the fact that, in the absence of information about how others are doing, highly competent subjects assume that others are performing
as well as they are.
Ross, L., Greene, D. & House, P. (1977). The false consensus effect: An egocentric bias in social perception and attributional processes.
Journal of Experimental Social Psychology, 13, 279-301.
- December 4, 2001
- Halo Effect
The extension of an overall impression of a person (or one particular outstanding trait) to
influence the total judgment of that person. The effect is to evaluate an individual high on many
traits because of a belief that the individual is high on one trait. Similar to this is the 'devil
effect', whereby a person evaluates another as low on many traits because of a belief that the
individual is low on one trait which is assumed to be critical.
E L Thorndike, "A Constant Error on Psychological Rating', Journal of Applied Psychology,
vol. IV (1920), 25-29
- November 9, 2001
- Infinite-Monkey Theorem
"If you put an infinite number of monkeys at typewriters, eventually one will bash out the script for Hamlet." (One may also hypothesize a small number of
monkeys and a very long period of time.) This theorem asserts nothing about the intelligence of the one random monkey that eventually comes up with the script
(and note that the mob will also type out all the possible incorrect versions of Hamlet). It may be referred to semi-seriously when justifying a brute force method;
the implication is that, with enough resources thrown at it, any technical challenge becomes a one-banana problem. This argument gets more respect since Linux
justified the bazaar mode of development.
This theorem was first popularized by the astronomer Sir Arthur Eddington. It became part of the idiom of techies via the classic SF short story "Inflexible Logic"
by Russell Maloney, and many younger hackers know it through a reference in Douglas Adams's "Hitchhiker's Guide to the Galaxy". On 1 April 2000 the usage
acquired its own Internet standard, RFC2795 (Infinite Monkey Protocol Suite).
Eric S. Raymond (compiler), New
Hacker's Dictionary (The MIT Press, Cambridge, M.A., 1996)
- July 31, 2001
- Moore's Law
Gordon Moore made his famous observation in 1965, just four years after the first planar integrated circuit was discovered. The press called it "Moore's Law" and the name has stuck. In his original paper, Moore predicted that the number of transistors per integrated circuit would double every 18 months. He forecast that this trend would continue through 1975. Moore's Law has been maintained for far longer, and still holds true today.
Intel Corp. Moore's Law. URL: http://www.intel.com/research/silicon/mooreslaw.htm
- June 25, 2001
- Butterfly Effect
The flapping of a butterfly's wings in China could cause tiny atmospheric changes which over a period of time could effect weather patterns in New York.
Discovered by American meteorologist Edward Norten Lorenz in 1963, this term refers to a strange attractor (resembling the flapping wings of a butterfly) which is produced by a set of differential equations describing air flows in the atmosphere known as the Lorenz equations. In meteorological terms, this models the unpredictability of local weather patterns.
I. Peterson, The Mathematical Tourist (New York, 1988)
- June 16, 2001
- Golden Ratio
The proportion which results when a line segment is divided in such a way that the smaller is to the
larger as the larger is to the whole. Numerically, it is:
G = ( 5 - 1) / 2 = 0.618033988...
The inverse of this number:
 = (5 + 1) / 2 = 1 + G = 1.618033988...
is sometimes also referred to as the golden ratio (also called Golden mean or
Divine proportion).
A golden rectangle has the property that the ratio of the difference of the sides to the smaller
equals the difference of the sides to the larger; in classical aesthetic theory, this was considered
pleasing to the eye.
- May 11, 2001
- Benford's Law
Benford's Law (which was first stated by Simon Newcomb in 1881)
states that if you randomly select a number from a table of
physical constants or statistical data, the probability that the
first digit will be a "1" is about 0.301, rather than 0.1 as we
might expect if all digits were equally likely. In general, the
"law" says that the probability of the first digit being a "d"
is
log_10( 1+ (1/d) )
This implies that a number in a table of physical constants is more
likely to begin with a smaller digit than a larger digit. It was
published by Newcomb in a paper entitled "Note on the Frequency of Use
of the Different Digits in Natural Numbers", which appeared in The
American Journal of Mathematics (1881) 4, 39-40. It was re-discovered
by Benford in 1938, and he published an article called "The Law of
Anomalous Numbers" in Proc. Amer. Phil. Soc 78, pp 551-72.
http://www.seanet.com/~ksbrown/kmath302.htm
- May 2, 2001
- M-theory
The "M" stands for the mother of all theories, magic,
mystery, or matrix, depending on the source. It is an adaptation of
superstring theory developed by Ed Witten of Princeton and Paul
Townsend of Cambridge. Townsend and Witten's version could
potentially be the unified field theory sought by Einstein for the
last 40 years of his life: a simple equation that would reconcile
incompatible aspects of his theory of relativity and quantum theory
to explain the nature and behavior of all matter and energy.
Applications of this knowledge could, through unlocking nature's
secrets, enable future technologies that currently are only spoken of
within the realm of science fiction: an inexhaustible source of clean
energy, and time travel, for example.
Superstring theory (sometimes just called string theory) has as its
basic premise the belief that the four fundamental forces of nature
(gravity, electromagnetism, and strong and weak nuclear forces), as
well as all matter are simply different manifestations of a single
essence. This essence, the material making up all energy and matter,
is thought to consist of tiny (a hundred billion billion times
smaller than the nucleus of an atom) vibrating strings that exist in
a multi-dimensional (10 or 26 dimensions) hyperspace. The extra
dimensions (beyond the ones we recognize: three spatial dimensions
and time) are thought to be compactified, or curled up, into tiny
pockets inside observable space. The particular vibrations of the
strings within this multidimensional hyperspace are thought to
correspond to particles that form the basis of everything - all
matter and energy - in existence.
Whatis.com Word-of-the-Day: May 2, 2001
- April 22, 2001
- Game Theory
- Created by American mathematician John von Neumann from analyses of games of poker, this is the finding of optimal strategies in competitions or conflicts,
particularly those with only a finite number of outcomes. The theory has been applied to such diverse disciplines as business, animal behavior and war. It was also
used in the development of the H-bomb. It is still in use today in all aspects of decision-making behavior.
- Account of politics using the analogy of competitive games. Individuals and institutions pursue their rationally predicted maximum self-interests. They do so in a manner analogous to games players
trying to calculate not only their own advantages, but the likely moves of their opponents. The result, paradoxically, is frequently neither the
maximum individual nor the maximum collective self-interest.
1. J L von Neumann and O Morgenstern, Theory of Games and Economic Behaviour (Princeton, 1947)
2. Robert Adams, Foundations of Political Analysis (New York, 1979)
- April 8, 2001
- Lawyer Paradox
A lawyer teaches law to a student without fee on condition that the student will pay him when he qualifies and wins his first case. However,
when the student qualifies he takes up another profession. The lawyer sues him for his fees, on the grounds that if he wins, he is paid and if he
loses, the student has won and so must pay by the agreement. The student in unperturbed because if he wins he need not pay the fees, and if
he loses he does not owe them. There is some confusion concerning the agreement here, but logical rules preventing the application of a
condition to itself certainly resolve the paradox.
Ascribed to the sophist philosopher Protagoras (c. 490-420 BC).
- April 2, 2001
- Red Queen Principle
For an evolutionary system, continuing development is needed just in order to maintain its fitness relative to the systems it is co-evolving with.
This principle was proposed by the evolutionary biologist L. van Valen (1973), and is based on the observation to Alice by the Red Queen in Lewis Carroll's Through the Looking Glass that "in this place it takes all the running you can do, to keep in the same place."
Van Valen L. (1973): "A New Evolutionary Law", Evolutionary Theory 1, p. 1-30.
- March 23, 2001
- Metcalfe's Law
The power of the network increases exponentially by the number of computers connected to it. Therefore, every computer added to the network both uses it as a resource while adding resources in a spiral of increasing value and choice. (possibly original version)
The value of a network grows by the square of the size of the network. (commonly expressed)
Robert M. Metcalfe, Ph.D.
- March 15, 2001
- Godwin's Law
[Usenet] "As a Usenet discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one." There is a tradition in many groups that, once this occurs, that thread is over, and whoever mentioned the Nazis has automatically lost whatever argument was in progress. Godwin's Law thus practically guarantees the existence of an upper bound on thread length in those groups. However there is also a widely- recognized codicil that any intentional triggering of Godwin's Law in order to invoke its thread-ending effects will be unsuccessful.
Eric S. Raymond (compiler), New
Hacker's Dictionary (The MIT Press, Cambridge, M.A., 1996)
- March 8, 2001
- Hanlon's Razor
A corollary of Finagle's Law,
similar to Occam's Razor that reads "Never attribute to malice
that which can be adequately explained by stupidity." The
derivation of the Hanlon eponym is not definitely known, but a very
similar remark ("You have attributed conditions to villainy that
simply result from stupidity.") appears in "Logic of Empire",
a classic 1941 SF story by Robert A. Heinlein, who calls it the
`devil theory' of sociology. Heinlein's popularity in the hacker
culture makes plausible the supposition that `Hanlon' is derived
from `Heinlein' by phonetic corruption. A similar epigram has been
attributed to William James, but Heinlein more probably got the
idea from Alfred Korzybski and other practitioners of General
Semantics. Quoted here because it seems to be a particular
favorite of hackers, often showing up in sig blocks,
fortune cookie files and the login banners of BBS systems and
commercial networks. This probably reflects the hacker's daily
experience of environments created by well-intentioned but
short-sighted people. Compare Sturgeon's Law ,
Ninety-Ninety Rule.
Eric S. Raymond (compiler), New
Hacker's Dictionary (The MIT Press, Cambridge, M.A., 1996)
- February 11, 2001
- Gestalt Theory
"Gestalt" is a German term which has no direct translation, but it is taken to mean any of the
following: form, configuration, shape and essence. Gestalt psychology takes the view that
phenomena should be studied and treated as a whole rather than on an elemental or componential
basis. A maxim developed from this theory is that the whole is different from the sum of its parts.
The forerunners of Gestalt Psychology were the German Max Wertheimer (1880-1943), Wolfgang
Kohler (1887-1967), and Kurt Koffka (1886-1941).
A D Ellis, ed., A Sourcebook of Gestalt Psychology (London, 1938)
- February 4, 2001
- Fibonacci Numbers
Named after Italian mathematician Leonardo Fibonacci - also known as Leonardo of Pisa - who
introduced the Arabic number system to Europe. It is a sequence of integers
0, 1, 1, 2, 3, 5, 8, 13, 21, 34 ...
with the property that each number in the sequence is the sum of the previous two. These numbers
arise in many applications in mathematics and in life sciences.
Leonardo Fibonacci (c.1170-1250)
- January 22, 2001
- Occam's Razor (principle of parsimony)
Principle that one should not multiply entities unnecessarily, or make further assumptions than are needed, and
in general that one should pursue the simplest hypothesis.
Adoption of this principle, though seemingly obvious, leads to problems about the role of simplicity in science,
especially when we are choosing between hypotheses that are not (or are not known to be) equivalent. There are
often different and clashing criteria for what is the simplest hypothesis, and it is not clear whether a simpler
hypothesis is pro tanto more likely to be true; and if not, what justification other than laziness there is
for adopting it.
Philosophy of Science (1961); journal containing symposium on simplicity
- January 16, 2001
- Veil of Ignorance
Conditions for just social life can be sketched if people are imagined in an "original position" where they decide upon social rules whilst behind a "veil of
ignorance" which prevents their knowing anything about their own situation in the hypothesized society.
Element in the theory of justice of American political theorist John Rawls (1921- ).
David Miller et al., eds, The Blackwall
Encyclopedia of Political Thought (Oxford, 1987).
- December 28, 2000
- Electric Speed
"At no period in human culture have men understood the psychic mechanisms
involved in invention and technology. Today it is the instant speed of electric
information that, for the first time, permits easy recognition of the patterns
and the formal contours of change and development. The entire world, past and
present, now reveals itself to us like a growing plant in an enormously
accelerated movie. Electric speed is synonymous with light and with the
understanding of causes."
McLuhan, Marshall, Understanding
Media: The Extensions of Man (Cambridge: MIT Press, 1996), 353.
- December 7, 2000
- Ninety-Ninety Rule
"The first 90% of the code accounts for the first 90% of the development time. The remaining 10% of the code accounts for the other 90% of the
development time." Attributed to Tom Cargill of Bell Labs, and popularized by Jon Bentley's September 1985 "Bumper-Sticker Computer
Science" column in "Communications of the ACM". It was there called the "Rule of Credibility", a name which seems not to have stuck. Other
maxims in the same vein include the law attributed to the early British computer scientist Douglas Hartree: "The time from now until the
completion of the project tends to become constant."
Eric S. Raymond (compiler), New
Hacker's Dictionary (The MIT Press, Cambridge, M.A., 1996)
- December 1, 2000
- Aristotle's four causes
Theory derived from the work of Greek philosopher Aristotle (384-322 BC). "Cause" is
a misleading, but traditional, translation of a word meaning "factor responsible," or perhaps
"explanatory factor."
The "four causes" provide answers to four questions one might ask about something, for example,
a man: "What is it made from?" "Flesh and so on" (material cause); "What is its form or
essence?" "A two-legged creature capable of reason (say)," (formal cause); "What
produced it?" "The father (on Aristotle's biology)" (efficient cause); "For what
purpose?" "To fulfill the function of a man (roughly meaning "to live a life in accordance with
reason") (final cause).
The doctrine, or parts of it, can then be extended in various ways (in particular to
cover events and states as well as objects), and undergoes various complications in the process;
but its primary application is to objects, especially biological objects and artifacts. The four
causes, especially the first two, are closely linked to Aristotle's important dichotomy between
matter and form (HYLOMORPHISM).
Aristotle, Physics,
book 2
- November 19, 2000
- Peter principle
Named after Canadian sociologist Laurence Peter (1920-90), who conducted extensive research into
business organizations, the principle states that in an organization, people are promoted to the level
of their incompetence and remain there.
L Peter and R Hull, The Peter
Principle: Why Things Always Go Wrong (London, 1969).
- November 12, 2000
- Law of Time and Chaos
In a process, the time interval between salient events (i.e., events that change
the nature of the process, or significantly affect the future of the process) expands
or contracts along with the amount of chaos.
Ray Kurzweil, The Age of Spiritual Machines: When Computers Exceed Human Intelligence (Penguin Putnam Inc.,
New York, New York, 1999).
- November 5, 2000
- Murphy's Law
The correct, original Murphy's
Law reads: "If there are two or more ways to do something, and one
of those ways can result in a catastrophe, then someone will do
it." This is a principle of defensive design, cited here because
it is usually given in mutant forms less descriptive of the
challenges of design for lusers.
For example, you don't make a
two-pin plug symmetrical and then label it `THIS WAY UP'; if it
matters which way it is plugged in, then you make the design
asymmetrical (see also the anecdote under magic smoke).
Edward A. Murphy, Jr. was one of the engineers on the rocket-sled
experiments that were done by the U.S. Air Force in 1949 to test
human acceleration tolerances (USAF project MX981). One experiment
involved a set of 16 accelerometers mounted to different parts of
the subject's body. There were two ways each sensor could be glued
to its mount, and somebody methodically installed all 16 the wrong
way around. Murphy then made the original form of his
pronouncement, which the test subject (Major John Paul Stapp)
quoted at a news conference a few days later.
Within months `Murphy's Law' had spread to various technical
cultures connected to aerospace engineering. Before too many years
had gone by variants had passed into the popular imagination,
changing as they went. Most of these are variants on "Anything
that can go wrong, will"; this is correctly referred to as
Finagle's Law.
The memetic drift apparent in these mutants
clearly demonstrates Murphy's Law acting on itself!
Eric S. Raymond (compiler), New
Hacker's Dictionary (The MIT Press, Cambridge, M.A., 1996)
- October 28, 2000
- Sleeper Effect
Identified by the American psychologist C I Hovland (1912-61). This effect was devised to describe the 'hidden'
impact that a mass communication or propaganda message can have on its audience. The attitude change
produced by the message is frequently not detectable until a period of time has passed, hence the term 'sleeper
effect'.
C I Hovland, A A Lumsdaine and F D Sheffield, Expriments in Mass Communication
(Princeton, N.J., 1949)
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