Classification of Intelligence: Addressing the Misconceptions and Benefits

“Allegory of Intelligence”, by Cesare Dandini

In our society today, “intelligence” is often referred to colloquially; few understand the cognitive complexities and nuances behind this commonly used term. By correcting misconceptions and encouraging a more thorough understanding of intelligence and its classifications, our society will be better equipped to fight cognitive disorders.

The general population’s idea of intelligence is mostly related to the ability to take in an array of information and apply it usefully, such as in making predictions in familiar and unfamiliar situations and responding accordingly. In truth however, this definition is what is scientifically referred to as “social intelligence,” and it is only a subset of what the term “intelligence” actually includes1.

The term “intelligence” encompasses far more than what is implied in its colloquial usage. In the scientific community, general intelligence is defined by the brain’s cognitive abilities. Psychologists have dubbed these facets of general intelligence as “g” 2. G is categorized into classifications by three cognitive functions: acquired knowledge, thinking abilities, or cognitive efficiency. By measuring competence in the five fields, scientists are able to roughly estimate one’s “intelligence level,” often also referred to as g level, for short 3.

The types of general intelligence are categorized into five categories: crystallized intelligence, fluid intelligence, visual processing, processing speed, and short-term memory.

The first element of cognition, acquired knowledge, includes crystallized intelligence (Gc). Gc measures skills built from a basis of formal education and practiced techniques. Gc is determined by the skills gained through training, education, and experience. Because experiences contribute largely to these forms of intelligence, one’s crystallized intelligence usually increases with age 3.

The second category, thinking ability, is measured by “raw brain power,” particularly those skills regarding problem solving, reasoning, and logic. Fluid intelligence (Gf), is another type of thinking ability allowing one to learn quickly in unfamiliar situations 4. Thinking ability also includes visual processing (Gv), which can also be referred to as visual-spatial intelligence. Gv controls the mind’s perception of images seen through the eye, most useful in the fields of engineering and architecture; an increased visual-spatial intelligence offers the ability to imagine objects in a different position than that in which they are seen 5.

Cognitive efficiency, the third category of G measures how effectively and efficiently our minds function. Processing speed and short-term memory (Gs and Gsm) are measured in this category 3.

Recent imaging studies have concluded that intelligence corresponds directly to how well information travels through the brain. By tracking the relay of signals through the neurons in each part of the brain, scientists are able to approximately measure where intelligence seems to be lacking or malfunctioning. 6. This signaling process corresponds directly to Gs and Gsm. Processing speed measures the efficiency of one’s mental processes, which is particularly applicable to tasks that demand high concentration, such as timed examinations including IQ tests and SAT exams 7.

Symptoms of low processing speed are easily detectable, such as decreased concentration levels and the tendency to be easily distracted. Similarly, because short-term memory is utilized in all social interactions, symptoms of memory loss are easily detectable. Our brains hold a limited amount of information for periods at a time. Because this storage ability is so crucial to our everyday lives and is constantly being utilized, short-term memory is classified as a subset of working memory. When one’s brain has a larger capacity for memory, it is able to process information more quickly; with more processing power, one may expand his short-term memory capacity to commit information to the memory more quickly. In contrast to long-term memory, short-term memory is most commonly measured through examination 8.

The importance of the classification of intelligence lies largely in the search for effective testing and examination methods. With intelligence divided into categories, each with numerous subsets, the measurements of general intelligence can only be estimates, as with IQ tests that measure one’s “intelligence quotient.” This standardized test measures analytical, mathematical, and spatial skills. In this sense, the IQ measures, in its major components, crystallized and fluid intelligence, visual processing, and processing speed, touching base with the three subsets of intelligence: acquired knowledge, thinking abilities, and cognitive efficiency 3.

As for quantitative intelligence, students are given midterms, homework, and finals to assess their performance ability in different areas. Studies show that as an overall average, estimated general intelligence peaks in the twenties and thirties. With more than 26 percent of American adults battling mental disorders each year, the awareness of intelligence, as scientifically defined and classified, can help discover cognitive disorders at their early stages 9.

A comprehensive understanding of intelligence helps scientists isolate mental disorders including obsessive-compulsive disorder (OCD), schizophrenia, social phobia, and generalized anxiety disorder (GAD). Knowledge of the factors and classifications of intelligence will also continue to help classify cognitive disorders accordingly. For example, attention deficit hyperactivity disorder shows a lacking of fluid intelligence as well as general intelligence, regarding difficulties with logical thinking, and lack of composure in social situations. The study of fluid and general intelligence contributed to this discovery 10.

A 2005 Yale University Medical School study showed that the earlier schizophrenia is caught and treated, the better the chance of recovery 5. Simply a comprehensive knowledge of intelligence can help discover a serious problem, such as schizophrenia or a social phobia disorder. A study from the Harvard School of Public Health in 1996 also stated that schizophrenia ranks among the top ten causes of disability in developed countries across the globe. Education on cognition will greatly impact these countries simply by early recognition 11. Similarly, ADHD, another disorder resulting from low processing speed (Gs) is also impacted positively by early recognition.

Though some disorders remain latent longer than others, knowledge of the facets of intelligence helps us better categorize and understand intelligence, the norms of intelligence levels over an average lifespan, and how to develop necessary and desired cognitive skills. In the future, the definite classification of intelligence will continue to help us isolate and fight mental disorders. Cognitive disorders cannot be ignored, and an understanding of intelligence will help those in and out of the scientific community fight them in time.


  1. Sterelny K, Social intelligence, human intelligence, and niche construction. J Philosophical Transactions of the Royal Society 2007; 362(1480): 720, 729, 731.
  2. Chrisley R, Beeger S. Artificial Intelligence: Critical concepts 2000; 2:260, 454.
  3. The 5 Factors of Intelligence Over the Lifespan. 2011
  4. Jaeggi SM, Buschkuehl M, Jonides J, Perrig Wj. Improving fluid intelligence with training on working memory. J PNAS 2008; 105(19): 6830, 6832.
  5. Wachs H, Visual-spatial thinking: An aspect of science overlooked by educators. 1999; 83(1):1.
  6. Brain Network Related To Intelligence Identified. 2007
  7. Jensen AR, The g Factor: The science of mental ability. 1998: 230, 231.
  8. Passolunghi, Chiara and Siegel,, Linda S. Short-Term Memory, Working Memory, and Inhibitory Control in Children with Difficulties in Arithmetic Problem Solving. 2002. Print.
  9. Statistics related to mental health disorders. 2011
  10. Jensen AR, Attention Deficit Hyperactivity Disorder (ADHD). A.D.A.M. Medical Encyclopedia. 2011.
  11. Vorvick LV, Schizophrenia. A.D.A.M Medical Encyclopedia. 2011.
  12. Image credit (Creative Commons): Moren j. EEG. Flickr. 2011 Jan 6.

Vasudha Rengarajan is a high school student at The Harker School. Follow The Triple Helix Online on Twitter and join us on Facebook.