What is it?
The scientific idea of general intelligence, often called ‘g’, was initially introduced by Charles Spearman in 1904. According to Spearman, people have varying amount of general intelligence that are used in most cognitive tasks. Often overlooked, Spearman also proposed that there are specific intelligences that are used within particular areas that are not related to other cognitive tasks. For example, a specific intelligence may be a high verbal ability that helps a person articulate and share his or her thoughts. This verbal ability may not be related to that person’s ability to navigate through an unfamiliar city.
Although it has been much maligned in recent years outside the research field and much more needs to be known, g remains relatively strongly supported by research findings.
According to g theory, differences observed in scores on various tests of intelligence or achievement are due to differences in general ability and differences in the specific abilities called upon by each of the tests.
More recent theories of general intelligence create a hierarchy with general intelligence at the top level and several broad abilities underneath (e.g., visual and auditory processing, memory), each of which has several more specific components underneath those.
Why do we care?
Intelligence test scores predict things like long-term performance in school, how much schooling one will receive, and what type of job one will get. Obviously, these things are not completely independent from intelligence test scores (i.e., getting a high score on an intelligence test will open opportunities for additional education, which also opens opportunities for better careers).
There have also been findings of a negative relationship between intelligence and criminal activity.
Can intelligence change?
As a parent, you may wonder whether intelligence can change. Life experiences matter. At an extreme example: a child raised entirely in one bare room without interacting with other people or the outside world would surely differ from a child raised by numerous experienced caregivers supplied with ample resources. This should not be interpreted to mean that a person growing up with fewer resources won’t amount to anything or that a child growing up with many resources will grow up to cure cancer. Rather, environments matter and can greatly help or hinder development. Research has shown that starting school sooner and staying in school longer are both associated with higher intelligence test scores. Moreover, time away from school (even if it is just summer vacation) is associated with a decline in intelligence test scores. These findings underscore the malleability of intelligence.
Many schools identify giftedness through measures of general intelligence, whereas others identify based on more subject-specific performance or ability. The extent to which one is the “right” way depends on how closely identification matches the curricula offered in that particular program.