One or several types of intelligence?
Some experts accept the concept of a single dominant factor of intelligence, general mental ability or g, while others argue that intelligence consists of a set of relatively independent abilities (American Psychological Association task force report, Gottfredson 1998). A single factor is not guaranteed. Other psychological tests which do not measure cognitive ability, such as personality tests, generate multiple factors.
Proponents of multiple-intelligence theories often claim that g is, at best, a measure of academic ability. Other types of intelligence, they claim, might be just as important outside of a school setting. One theory even suggests the existence of two types of g (see Fluid and crystallized intelligence).
Yale psychologist Robert J. Sternberg has proposed a Triarchic Theory of Intelligence. Harvard psychologist Howard Gardner's theory of multiple intelligences breaks intelligence down into at least eight different components: logical, linguistic, spatial, musical, kinesthetic, naturalist, intra-personal and inter-personal intelligences. Daniel Goleman and several other researchers have developed the concept of emotional intelligence and claim it is at least as important as more traditional sorts of intelligence.
In response, g theorists have pointed out that g's predictive validity has been repeatedly demonstrated, for example in predicting important non-academic outcomes such as job performance (see IQ), while no multiple-intelligences theory has shown comparable validity. Meanwhile, they argue, the relevance, and even the existence, of multiple intelligences have not been borne out when actually tested (Hunt 2001).
The fundamental indicator of a general factor is that test scores on a wide range of seemingly unrelated cognitive ability tests (such as sentence completion, arithmetic, and memorization) are positively correlated. People who score highly on one test tend to score highly on all of them. This suggests that the tests are not unrelated, but that they all tap a common factor. The common factor, g, can be extracted using mathematical techniques such as factor analysis or principal components analysis. IQ tests measure g better than any other test. According to Jeff Hawkins, the brain's cortex implements a memory prediction system to form the basis of intelligence.
Controversies
Researchers in the field of human intelligence have encountered a considerable amount of public concern and criticism - much more than many scientists would be accustomed to or comfortable with (for examples, see Gottfredson, 2005). Some of the controversial topics include:
- the relevance of psychometric intelligence to the common-sense understanding of the topic.
- the importance of intelligence in everyday life (see IQ).
- the genetic and environmental contributions to individual variation in intelligence (see Nature versus nurture).
- differences in average measured intelligence between different groups and the source and meaning of these differences (see Race and intelligence and Sex and intelligence).
Collective and non-human intelligence
Some thinkers have explored the idea of collective intelligence, arising from the coordination of many people. A battleship, for instance, cannot be operated by a single person's knowledge, actions and intelligence, it takes a coordinated and interacting crew. Similarly, the interesting behaviors of a bee colony are not exhibited in the intelligence and actions of any single bee, but rather manifested in the behavior of the hive. These ideas are explored as a basis for human thought, with applications for artificial intelligence (AI), by MIT AI pioneers Norbert Wiener and Marvin Minsky. Artificial intelligence (AI) has emerged from Computer science as a specialty which seeks to make computers act in increasingly intelligent ways, and provides insights into human thought processes.
When considering animal intelligence, a more general definition of intelligence might be applied: the "ability to adapt effectively to the environment, either by making a change in oneself or by changing the environment or finding a new one" (Encyclopædia Britannica). Many people have also speculated about the possibility of extraterrestrial intelligence.
