Intelligence involves the ability to adapt to one’s environment and the capacity to learn from experience.

Theories of Intelligence

Francis Galton was the first to propose a theory of intelligence. Galton believed intelligence had a biological basis that could be studied by measuring reaction times to certain cognitive tasks. Intelligence Quotient (IQ) was first used by German psychologist William Stern to quantitatively measure intelligence.

Edward Thorndike in 1920 theorized three types of intelligence: social, mechanical, and abstract. Thorndike defined social intelligence as the ability to manage and understand people. He focused on behavior rather than consciousness in his research; as such, his studies constituted the beginning of investigations related to social intelligence.

In 1983, Howard Gardner published a book on multiple intelligence that breaks intelligence down into at least eight different modalities: logical, linguistic, spatial, musical, kinesthetic, naturalist, interpersonal, and intrapersonal intelligence.

In 1990, Peter Salovey and John Mayer coined the term “emotional intelligence” and defined it as “the ability to monitor one’s own and others’ feelings, to discriminate among them, and to use this information to guide one’s thinking and actions.

Genetic and Environmental Impacts on Intelligence

Genetics and the environment are so intertwined in their influence on human intelligence that it remains difficult to determine which, if either, is most responsible for determining a person’s intelligence.

Intelligence is generally considered to be even more complicated to trace to one source because it is a polygenic trait, influenced by many interacting genes. Up to 80% of the variation found in adult human intelligence is thought to be attributable to genetics, even though it is a complicated, polygenic trait.

Genetic causes for many learning disabilities, such as dyslexia, and neural disorders, such as Down syndrome, autism, and Alzheimer’s disease have been investigated by the field of cognitive genomics, the study of genes as they relate to human cognition.

Many different environmental influences have been found to shape intelligence. These influences generally fall into two main categories: biological and sociocultural. Biological influences act on the physical body, while sociocultural influences shape the mind and behavior of an individual.

Biological influences include everything from nutrition to stress and begin to shape intelligence from prenatal stages onward. Nutrition has been shown to affect intelligence throughout the human lifespan; malnutrition during critical early periods of growth can harm cognitive development. Inadequate nutrition can disrupt neural connections and pathways, and leave a person unable to recover mentally.

Sociocultural influences also impact on intelligence. The family unit is one of the most basic influences on child development, but it is difficult to untangle the genetic from the environmental factors in a family. For example, the quantity of books in a child’s home has been shown to positively correlate with intelligence.

Extremes of intelligence

Intelligence can be viewed as a spectrum with extremes, whilst most of the population will fall into the middle of the distribution there are extremes at either end, those who are intellectually disabled through to those that are intellectually gifted.

Individuals are classified as having an intellectual disability if they score below 70 on a measure of intelligence, display deficits in adaptive functioning, have impairments in at least two areas of functioning (such as self-care or social skills), and experience the onset of one or more of these factors before age 18. The most common causes of intellectual disability are fetal alcohol syndrome and Down syndrome. Individuals with intellectual disabilities face both personal and external challenges in life. In addition to challenges in cognitive functioning and daily living, people with intellectual disabilities are often stigmatized and devalued by society.

At the other end of the spectrum are intellectually gifted. A child whose cognitive abilities are markedly more advanced than those of his or her peers is considered intellectually gifted. Gifted children often learn faster than their peers and work independently. Gifted programs can be beneficial by keeping gifted children engaged in learning and providing them with opportunities to discover their full potential. Gifted programs can, however, be detrimental by labeling children as either “gifted” or “not gifted,” which can, in turn, create a self-fulfilling prophecy where “not gifted” students do not put forth the same effort and therefore are not as successful.

Practice Questions

MCAT Official Prep (AAMC)

Section Bank P/S Section Passage 2 Question 9

Sample Test P/S Section Passage 4 Question 17

Practice Exam 2 P/S Section Question 45

Key Points

• Theories on intelligence have evolved over the last century from simple measures of biological responses to IQ tests to encompassing multiple intelligences.

• Intelligence is influence by genetics and environmental factors that can increase intelligence over time or cause a decrease

• Intelligence has two extremes those that are intellectually disabled and struggle with general cognitive tasks, caused by genetic or environmental factors and those that are intellectually gifted and excel in cognitive tasks.

Key Terms

Sociocultural: of or relating to both society and culture

Emotional intelligence: the ability, capacity, or skill to perceive, assess, and manage the emotions of oneself, of others, and groups

Social intelligence: the ability to understand and manage men and women, boys and girls; to act wisely in human relations

Intelligence: capacity of mind, especially to understand principles, truths, facts or meanings, acquire knowledge, and apply it to practice; the ability to learn and comprehend

Intelligence quotient: an assessment on intelligence

Alzheimer’s disease: an irreversible, progressive brain disorder that slowly destroys memory and thinking skills, and eventually the ability to carry out the simplest tasks

Polygenic trait: refers to a trait that is controlled by multiple non-allelic genes

Down syndrome: a condition in which a person has an extra chromosome impacting cognitive development