intelligence, in psychology, the general mental ability involved in calculating, reasoning, perceiving relationships and analogies, learning quickly, storing and retrieving information, using language fluently, classifying, generalizing, and adjusting to new situations. Alfred Binet, the French psychologist, defined intelligence as the totality of mental processes involved in adapting to the environment. Although there remains a strong tendency to view intelligence as a purely intellectual or cognitive function, considerable evidence suggests that intelligence has many facets.

Early investigations into intelligence assumed that there was one underlying general factor at its base (the g-factor), but later psychologists maintained that intelligence could not be determined by such a simplistic method. Raymond Cattell argued that intelligence can be separated into two fundamental parts: fluid ability and crystallized ability. Fluid ability is considered innate, basic reasoning skill, while crystallized intelligence is the information and skills that are acquired through experience in a cultural environment. Other psychologists have further divided intelligence into subcategories. Howard Gardner maintained (1985) that intelligence is comprised of seven components: musical, bodily-kinesthetic, logical-mathematical, linguistic, spatial, interpersonal, and intrapersonal. J. P. Guilford tried (1982) to show that there are 150 different mental abilities that constitute intelligence.

It is generally accepted that intelligence is related to both heredity and environment. Studies done on families, particularly among identical twins and adopted children, have shown that heredity is an important factor in determining intelligence; but they have also suggested that environment is a critical factor in determining the extent of its expression. For instance, children reared in orphanages or other environments that are comparatively unstimulating tend to show retarded intellectual development. In recent years, controversy regarding intelligence has centered primarily around how much of each factor, heredity and environment, is responsible for an individual's level of intelligence.

Intelligence Tests

Although a strict definition of intelligence has proven elusive, a number of psychologists have argued that it can be quantified, primarily through testing. In 1905, Alfred Binet and Theodore Simon devised a system for testing intelligence, with scoring based on standardized, average mental levels for various age groups. In 1916 the Binet-Simon Intelligence Scale was expanded and reworked by Lewis Terman at Stanford Univ., and later revisions called the Revised Stanford-Binet Intelligence Tests were published in 1937, 1960, and 1985. A highly successful series of tests, designed by psychologist David Wechsler, have been in wide use for years as diagnostic and evaluative instruments. Known in 1939 as the Wechsler-Bellevue Intelligence Scale, the Wechsler Adult Intelligence Scale is a standard tool for intelligence testing today. All of these tests are administered to one individual at a time by a psychometrician. While no consensus of opinion prevails about what such tests actually measure, their use in education has had great practical value in assigning children to suitable class groups and in predicting academic performance.

The Army Alpha Test, which was first administered to nearly 2 million new recruits in World War I, and the Otis Group Intelligence Scale, were forerunners of many other group tests that are administered economically and quickly to large numbers, and were thus effective for use in schools and industry. National, standardized group tests are administered for college and graduate school entrance, and for a number of civil service positions.

The work of Binet, Terman, and Wilhelm Stern paved the way for a method of classifying intelligence in terms of a standardized measure, with standardization ensured by the large number of individuals of various ages taking the test. German psychologist L. Wilhelm Stern was the first to coin the term intelligence quotient (IQ), a figure derived from the ratio of mental age to chronological age. Although Stern's method for determining IQ is no longer in common use, the term IQ is still used today to describe the results in several different tests. Today, an average IQ score is considered to be 100, with deviations based on this figure. Mentally retarded individuals usually score below 70 in IQ tests, and are classified according to functional ability through reference to a scale of low IQ scores.

One criticism of intelligence testing is that it is difficult to insure that test items are equally meaningful or difficult for members of different sociocultural groups. Testing is often considered validated in part, however, by the finding that the quantity measured by the tests can be closely correlated in American society with career and academic achievement. There has been a decline in interest in pure intelligence tests since the 1920s, with a corresponding increase in the number of mental tests that measure special aptitudes and personality factors (see psychological tests).

artificial intelligence (AI), the use of computers to model the behavioral aspects of human reasoning and learning. Research in AI is concentrated in some half-dozen areas. In problem solving, one must proceed from a beginning (the initial state) to the end (the goal state) via a limited number of steps; AI here involves an attempt to model the reasoning process in solving a problem, such as the proof of a theorem in Euclidean geometry. In game theory (see games, theory of), the computer must choose among a number of possible "next" moves to select the one that optimizes its probability of winning; this type of choice is analogous to that of a chess player selecting the next move in response to an opponent's move. In pattern recognition, shapes, forms, or configurations of data must be identified and isolated from a larger group; the process here is similar to that used by a doctor in classifying medical problems on the basis of symptoms. Natural language processing is an analysis of current or colloquial language usage without the sometimes misleading effect of formal grammars; it is an attempt to model the learning process of a translator faced with the phrase "throw mama from the train a kiss." Cybernetics is the analysis of the communication and control processes of biological organisms and their relationship to mechanical and electrical systems; this study could ultimately lead to the development of "thinking" robots (see robotics). Machine learning occurs when a computer improves its performance of a task on the basis of its programmed application of AI principles to its past performance of that task.

In the public eye advances in chess-playing computer programs have become symbolic of progress in AI. In 1948 British mathematician Alan Turing developed a chess algorithm for use with calculating machines—it lost to an amateur player in the one game that it played. Ten years later American mathematician Claude Shannon articulated two chess-playing algorithms: brute force, in which all possible moves and their consequences are calculated as far into the future as possible; and selective mode, in which only the most promising moves and their more immediate consequences are evaluated. In 1988 Hitech, a program developed at Carnegie-Mellon Univ., defeated former U.S. champion Arnold Denker in a four-game match, becoming the first computer to defeat a grandmaster. A year later, Gary Kasparov, the reigning world champion, bested Deep Thought, a program developed by the IBM Corp., in a two-game exhibition. In 1990 the German computer Mephisto-Portrose became the first program to defeat a former world champion; while playing an exhibition of 24 simultaneous games, Anatoly Karpov bested 23 human opponents but lost to the computer. Kasparov in 1996 became the first reigning world champion to lose to a computer in a game played with regulation time controls; the Deep Blue computer, developed by the IBM Corp., won the first game of the match, lost the second, drew the third and fourth, and lost the fifth and sixth. Deep Blue used the brute force approach, evaluating more than 100 billion chess positions each turn while looking six moves ahead; it coupled this with the most efficient chess evaluation software yet developed and an extensive library of chess games it could analyze as part of the decision process. Subsequent matches between Vladimir Kramnik and Deep Fritz (2002, 2006) and Kasparov and Deep Junior (2003) have resulted in two ties and a win for the programs. Unlike Deep Blue, which was a specially designed computer, these more recent computer challengers are chess programs that run on powerful personal computers. Such programs have become an important tool in chess, and are used by chess masters to analyze games and experiment with new moves.

Wechsler Adult Intelligence Scale (WAIS): see psychological tests.

Central Intelligence Agency (CIA), independent executive bureau of the U.S. government established by the National Security Act of 1947, replacing the wartime Office of Strategic Services (1942-45), the first U.S. espionage and covert operations agency. While the CIA's covert operations receive the most attention, its major responsibility is to gather intelligence, in which it uses not only covert agents but such technological resources as satellite photos and intercepted telecommunications transmissions. The CIA was given (1949) special powers under the Central Intelligence Act: The CIA director may spend agency funds without accounting for them; the size of its staff is secret; and employees, exempt from civil service procedures, may be hired, investigated, or dismissed as the CIA sees fit. Under the U.S. intelligence agency reorganization enacted in 2004, the CIA reports to the independent director of national intelligence, who is responsible for coordinating the work and budgets of all 15 U.S. intelligence agencies. To safeguard civil liberties in the United States, the CIA is denied domestic police powers; for operations in the United States it must enlist the services of the Federal Bureau of Investigation. Allen Welsh Dulles, director from 1953 to 1961, strengthened the agency and emboldened its tactics.

The CIA has often been criticized for covert operations in the domestic politics of foreign countries. The agency was heavily involved in the failed 1961 Bay of Pigs invasion of Cuba, deeply embarrassing the United States. In 1971 the U.S. government acknowledged that the CIA had recruited and paid an army fighting in Laos. In 1973 the CIA came under congressional investigation for its role in the Pentagon Papers case. The agency had provided members of the White House staff, on request, with a personality profile of Daniel Ellsberg, defendant in the Pentagon Papers trial in 1973, and had indirectly aided the White House "Plumbers," the special unit established to investigate internal security leaks. This direct violation of the National Security Act's prohibition led Congress to strengthen provisions barring the agency from domestic operations.

Its foreign operations came under attack in 1974 for involvement in Chilean internal affairs during the administration of Salvador Allende, and in 1986 it was shown to be involved in the Iran-Contra affair. Diminished in the early 1990s after the end of the cold war, it began rebuilding later in the decade, accelerating the process after the terror attacks of Sept. 11, 2001. It was subsequently hurt, however, by the revelation that Director George Tenet had insisted, prior to the Iraq invasion of 2003, that Iraq possessed weapons of mass destruction, and the quality of the intelligence that it had provided was criticized. One result of the intelligence failures relating to Sept., 2001, and Iraq was the reorganization of 2004, which demoted the director of the CIA and made the CIA one of several agencies overseen by the new position of director of national intelligence.

in full intelligence quotient

Number intended to represent a measure of relative intelligence as determined by the subject's responses to a series of test problems. The IQ was originally computed as the ratio of a person's mental age to his or her chronological (physical) age, multiplied by 100, but use of the concept of mental age has been largely discontinued, and IQ is now generally assessed on the basis of the statistical distribution of scores. The most widely used intelligence tests are the Stanford-Binet test (1916), for children, and the Wechsler test (1939), originally for adults but now also for children. A score above 130 is considered to reflect “giftedness,” while a score below 70 is considered to reflect mental impairment or intellectual disability. Intelligence tests have provoked great controversy, particularly about what kinds of mental ability constitute intelligence and whether IQ adequately represents these abilities, and about cultural and class bias in test construction and standardization procedures.

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In government and military operations, evaluated information concerning the strength, activities, and probable courses of action of international actors that are usually, though not always, enemies or opponents. The term also refers to the collection, analysis, and distribution of such information and to the secret intervention in the political or economic affairs of other countries, an activity commonly known as “covert action.” Intelligence is an important component of national power and a fundamental element in decision making regarding national security, defense, and foreign policies. It is conducted on three levels: strategic, tactical, and counterintelligence. Despite the public image of intelligence operatives as cloak-and-dagger secret agents, much intelligence work involves an undramatic search of “open” sources, such as radio broadcasts and various publications. Among covert sources of intelligence are imagery intelligence, which includes aerial and space reconnaissance, signals intelligence, which includes electronic eavesdropping and code breaking, and human intelligence, which involves the secret agent working at the classic spy trade. Leading national intelligence organizations are the Central Intelligence Agency (CIA) in the U.S.; the Federal Security Service in Russia; MI5 and MI6 in Britain; and the Mossad in Israel.

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Acquisition of trade secrets from business competitors. Industrial spying is a reaction to the efforts of many businesses to keep secret their designs, formulas, manufacturing processes, research, and future plans. Trade secrets may find their way into the open market through disloyal employees or through various other means. Penalties against those found guilty range from an injunction against further use of the knowledge to substantial damages. Seealso patent.

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Ability of a machine to perform tasks thought to require human intelligence. Typical applications include game playing, language translation, expert systems, and robotics. Although pseudo-intelligent machinery dates back to antiquity, the first glimmerings of true intelligence awaited the development of digital computers in the 1940s. AI, or at least the semblance of intelligence, has developed in parallel with computer processing power, which appears to be the main limiting factor. Early AI projects, such as playing chess and solving mathematical problems, are now seen as trivial compared to visual pattern recognition, complex decision making, and the use of natural language. Seealso Turing test.

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Principal intelligence and counterintelligence agency of the U.S., established in 1947 as a successor to the World War II-era Office of Strategic Services. The law limits its activities to foreign countries; it is prohibited from gathering intelligence on U.S. soil, which is a responsibility of the Federal Bureau of Investigation. Officially a part of the U.S. Defense Department, it is responsible for preparing analyses for the National Security Council. Its budget is kept secret. Though intelligence gathering is its chief occupation, the CIA has also been involved in many covert operations, including the expulsion of Mohammad Mosaddeq from Iran (1953), the attempted Bay of Pigs invasion of Cuba (1961), and support of the Nicaraguan contras in the 1980s.

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