What Is Intelligence And How Is It Measured?
Reading a road map upside-down, excelling at chess, and generating synonyms for "brilliant" may seem like three different skills. But each is thought to be a measurable indicator of general intelligence or "g," a construct that includes problem-solving ability, spatial manipulation, and language acquisition, and is relatively stable across a person's lifetime.
IQ tests compare a person's performance on the test with the performance of other people of the same age, often referred to as a normative sample. In children, the score reflects the difference between a child's mental and chronological age.
IQ—or intelligence quotient—is the score most widely used to assess general intelligence or "g," and typically measures a variety of skills from verbal to spatial. Any person from any walk of life can be highly intelligent, and scoring high on one aspect of intelligence tends to correlate with high scores in other aspects.
IQ is the most robust psychological trait measured and strongly correlates with positive life outcomes, including health and longevity, job performance, and adult income. It is also neuro-protective in ways that are not fully understood: People with high IQs are at an advantage in coping with traumatic events (they are less likely to develop full-blown PTSD and more capable of overcoming it when they do) and may experience less rapid decline in the course of Alzheimer's Disease.
Can Intelligence Be Improved?
Some aspects of intelligence can be improved; however, controversy engulfs how to improve intelligence and how much intelligence can evolve. Perhaps the most relevant maxim is “just because people can circumvent limits on performance does not mean that performance is without limits."
First, one critical prerequisite for intellectual growth is rejecting the belief that intelligence is fixed. Second, the aspects of intelligence that can be improved include processing speed, problem-solving strategies, and memory improvement. There is a much lower probability of improving overall IQ test performance or working memory capacity (a major correlate of intelligence).
The skills practiced in brain training apps are not readily transferable to either IQ test performance or to solving unique environmental challenges, and therefore have not demonstrable impact on IQ.
For more on the question of just how fixed or malleable are cognitive abilities, see here.
Are There Different Types of Intelligence?
Most psychologists view intelligence as one overall measure comprising a wide variety of skills, typically calculated through IQ tests. In the early 1980s, however, Harvard researcher Howard Gardner proposed that there may be multiple kinds of intelligence that humans possess in varying quantities.
These types, of which there are now 9, include visual-spatial, logical-mathematical, and interpersonal intelligence, among others. According to Gardner's theory, someone high in interpersonal intelligence would likely excel at cooperating within a group, while someone with high levels of logical-mathematical intelligence would have a heightened capacity to understand numbers, patterns, and logical reasoning.
But though the concept has gained steam with the wider public—and is often used in personality or employment tests—many intelligence researchers dispute the existence of different intelligences and have criticized Gardner's theory, criteria, and research designs.