The triarchic theory of intelligence was formulated by Robert J. Sternberg (Sternberg, 1985; Sternberg et al., 1995), a prominent figure in the research of human intelligence. The theory was among the first to go against the psychometric approach to intelligence and take a more cognitive approach.

Sternberg’s definition of human intelligence is “a mental activity directed toward purposive adaptation to, selection and shaping of, real-world environments relevant to one’s life” (Sternberg, 1985, p. 45), which means that intelligence is how well an individual deals with environmental changes throughout their lifespan.



Sternberg associated the workings of the mind with a series of components (Sternberg, 1985). They are:
1. Meta-components:  Executive processes used in problem solving and decision-making those involve the majority of managing our mind. They tell the mind how to act. Also sometimes referred to as a homunculus, a fictitious or metaphorical "person" inside our head that controls our actions, and which is often seen to invite an infinite regress of homunculi controlling each other (Sternberg, 1985).
2. Performance components: Processes that actually carry out the actions the meta-components dictate. These are the basic processes that allow us to do tasks, such as perceiving problems in our long-term memory, perceiving relations between objects, and applying relations to another set of terms (Sternberg, 1997).
3. Knowledge-acquisition components: Used in obtaining new information. These components complete tasks that involve selectively choosing information from irrelevant information and selectively combine the various pieces of information gathered. Gifted individuals are proficient in using these components because they are able to learn new information at a greater rate (Sternberg, 1997).

Whereas Sternberg explains that the basic information processing components underlying the three parts of his triarchic theory are the same, different contexts and different tasks require different kind of intelligence (Sternberg, 2001). According to the Triarchic theory, there are three basic types of human intelligence:

1. Componential or analytic intelligence: It involves the abilities to think critically and analytically. Analytical giftedness is influential in being able to take apart problems and being able to see solutions not often seen.
Persons high on this dimension usually excel on standard tests of academic potential and make excellent students. Professors are typically high on this aspect of intelligence.
Unfortunately, individuals with only this type are not as adept at creating unique ideas of their own. This form of giftedness is the type that is tested most often. (Sternberg, 1997).

2. Experiential or creative intelligence: It emphasizes insight and the ability to formulate new ideas. Persons who rate high on this dimension excel at zeroing in on what information is crucial in a given situation, and at combining seemingly unrelated facts.
This is the kind of intelligence shown by many scientific geniuses and inventors, such as Einstein, and Newton, and—some would say— Freud.
Sternberg splits the role of experience into two parts: novelty and automation. A novel situation is one that you have never experienced before. People that are adept at managing a novel situation can take the task and find new ways of solving it that the majority of people would not notice (Sternberg, 1997). A process that has been automated has been performed multiple times and can now be done with little or no extra thought. Once a process is automatized, it can be run in parallel with the same or other processes. The problem with novelty and automation is that being skilled in one component does not ensure that you are skilled in the other (Sternberg, 1997).

3. Contextual or practical intelligence: It “deals with the mental activity involved in attaining fit to context” (Sternberg, 1985, p. 45). It involves the ability to apply synthetic and analytic skills to everyday situations. Persons high on this dimension are often referred to as "street smarts."
Practically gifted people are superb in their ability to succeed in any setting (Sternberg, 1997). They use three processes to create an ideal fit between themselves and their environment:
a. Adaptation occurs when one makes a change within oneself in order to better adjust to one’s surroundings (Sternberg, 1985). Ex: when temperatures drop, people adapt by wearing extra layers of clothing to remain warm.
b. Shaping occurs when one changes their environment to better suit one’s needs (Sternberg, 1985). Ex: A teacher may invoke the new rule of raising hands to speak to minimize disruption during speaking.
c. Selection is undertaken when a completely new alternate environment is found to replace the previous, unsatisfying environment to meet the individual’s goals (Sternberg, 1985). Ex: Immigrants leave their homeland countries where they endure economical and social hardships and go to other countries in search of a better and less strained life.

Sternberg acknowledges that an individual is not restricted to having excellence in only one of these three intelligences. Many people may possess an integration of all three and have high levels of all three intelligences.

Challenges

Psychologist Linda Gottfredson (Gottfredson, 2003) criticises the unempirical nature of triarchic theory and argues that it is absurd to assert that traditional Intelligence tests are not measuring practical intelligence when they show a moderate correlation with income, especially at middle age when individuals have had a chance to reach their maximum career potential, an even higher correlation with occupational prestige, and that IQ tests even predict the ability to stay out of jail and stay alive (all of which qualifies as practical intelligence or "street smarts").

Gottfredson claims that what Sternberg calls practical intelligence is not a broad aspect of cognition at all but simply a specific set of skills people learn to cope with a specific environment (task specific knowledge).

There is evidence to suggest that certain aspects of creativity (i.e. Divergent thinking) are separable from analytical intelligence, and are better accounted for by the cognitive process of executive functioning. More specifically, task-switching and interference management are suggested to play an important role in divergent thinking. A more recent meta-Analysis found only small correlations between IQ and creativity (Kim, 2005).

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Growing evidence suggests that there is more to intelligence than the verbal, mathematical, and reasoning abilities that are often associated with academic success. Sternberg proposed a tri-archic theory comprised of three components. In his words, “You need creative intelligence to come up with an idea, analytical intelligence to know if it’s a good idea, and practical intelligence to sell it” (Sternberg). Depending on the context, different types of intelligence may be required by a person to succeed, or even survive.

Sources:
http://sites.psu.edu/caradorercl1314/2014/02/12/sternbergs-solution/
http://en.wikipedia.org/wiki/Triarchic_theory_of_intelligence
Psychology, Robert Baron (Click for free preview)