A general definition of ‘Intelligence’ is general cognitive ability, including problem solving skills, ability to reason, understand abstract and complex concepts and ideas, learn quickly and learn from experiences. In the 20th century there was increased research done on the role of genetics in behaviour. With Albert Binet developing an IQ test to measure Intelligence. There has been an ongoing debate regarding intelligence, whether it is inherited or result of an environment stimuli.
What influences behaviour more: Nature or Nurture? Is a question no one can answer definitively. With years going by and research being done the answer sways back and forth continuously.
In 1963, an influential article in Science reviewed family, twin, and adoption data for IQ scores and concluded that genetic influence is important (Erlenmeyer-Kimling & Jarvik, 1963). The twin studies of Steven Vandenberg on cognitive abilities in the 1960s confirmed the results of the earlier twin and adoption studies in pointing to genetic influence (Vandenberg, 1968). In 1969 when Arthur Jensen published a paper and suggested that there might be an average IQ differences between ethnic groups which may be due to genetic factors. Richard Herrnstein (1973) also suggested that IQ differences between classes might also be due to genetics as being in a socioeconomic upper class is a result of good genes.
In the 1980s with the advances made in molecular genetics, people started to be more interested and excited about this study. For example, a 1987 survey of around thousand social and behavioral scientists and educators concluded that most of them had accepted a significant role o in IQ scores (Snyderman & Rothman, 1987).
There is research that supports the claim that nature plays a role in intelligence. For example, there is research that proves that poverty influences the development of children’s intelligence. Also the statement made by John B. Watson: “Give me a dozen healthy infants and my own specified world to bring them up in, and I’ll guarantee to take anyone at random and train him to become any type of specialist I might select-doctor, lawyer, artist, merchant-chief, and, yes, even beggar and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors”.
However, with advances in research and technology, scientists have recently identified forty genes that influence intelligence. The research on 60,000 adults and 20,000 children uncovered 40 new genes that play a role in intelligence, which brings the total of the known genes that influence IQ to 52. This further proves that genetics does influence Intelligence and that intelligence is to some extent hereditary.
Wahlsten (1997) said the adoption studies conducted in France have found that by putting an infant from a low socio economic status to a home of high economic status improved the childhood IQ by 12 to 16 points. From this we can conclude that intelligence can be a result of both genetics and environment. It can be inferred that a combination of genes and environment produce intelligence.
WHAT IS INTELLIGENCE?
Despite a long history of research and debate, there is still no standard definition of intelligence. This has led some to believe that intelligence may be approximately described, but cannot be fully defined. A typical dictionary definition of intelligence is “the capacity to acquire and apply knowledge.” Intelligence includes the ability to benefit from past experience, act purposefully, solve problems, and adapt to new situations. Intelligence can also be defined as “the ability that intelligence tests measure.” There is a long history of disagreement about what actually constitutes intelligence.
Psychologists have long debated how to best conceptualize and measure intelligence (Sternberg, 2003). These questions include how many types of intelligence there are, the role of nature versus nurture in intelligence, how intelligence is represented in the brain, and the meaning of group differences in intelligence. Intelligence refers to one’s cognitive abilities, which include memory, comprehension, understanding, reasoning, and abstract thought.
Scientists generally agree that intelligence can be captured by psychometric tests. But the study of intelligence is dogged by questions of just how much IQ contributes to an individual’s success and well-being, how genes and environment interact to generate smarts and why the average IQ score rose throughout the world during the twentieth century.
In the early 1900s, the French psychologist Alfred Binet (1857–1914) and his colleague Henri Simon (1872–1961) began working in Paris to develop a measure that would differentiate students who were expected to be better learners from students who were expected to be slower learners. The goal was to help teachers better educate these two groups of students. Binet and Simon developed what most psychologists today regard as the first intelligence test, which consisted of a wide variety of questions that included the ability to name objects, define words, draw pictures, complete sentences, compare items, and construct sentences.
Binet and Simon (Binet, Simon, ; Town, 1915; Siegler, 1992) believed that the questions they asked their students, even though they were on the surface dissimilar, all assessed the basic abilities to understand, reason, and make judgments. And it turned out that the correlations among these different types of measures were in fact all positive; students who got one item correct were more likely to also get other items correct, even though the questions themselves were very different.
On the basis of these results, the psychologist Charles Spearman (1863–1945) hypothesized that there must be a single underlying construct that all of these items measure. He called the construct that the different abilities and skills measured on intelligence tests have in common the general intelligence factor (g). Virtually all psychologists now believe that there is a generalized intelligence factor, g, that relates to abstract thinking and that includes the abilities to acquire knowledge, to reason abstractly, to adapt to novel situations, and to benefit from instruction and experience (Gottfredson, 1997; Sternberg, 2003). People with higher general intelligence learn faster.
Soon after Binet and Simon introduced their test, the American psychologist Lewis Terman (1877–1956) developed an American version of Binet’s test that became known as the Stanford-Binet Intelligence Test. The Stanford-Binet is a measure of general intelligence made up of a wide variety of tasks including vocabulary, memory for pictures, naming of familiar objects, repeating sentences, and following commands.
Although there is general agreement among psychologists that g exists, there is also evidence for specific intelligence (s), a measure of specific skills in narrow domains. One empirical result in support of the idea of ‘s’ comes from intelligence tests themselves. Although the different types of questions do correlate with each other, some items correlate more highly with each other than do other items; they form clusters or clumps of intelligences.
One distinction is between fluid intelligence, which refers to the capacity to learn new ways of solving problems and performing activities, and crystallized intelligence, which refers to the accumulated knowledge of the world we have acquired throughout our lives (Salthouse, 2004). These intelligences must be different because crystallized intelligence increases with age—older adults are as good as or better than young people in solving crossword puzzles—whereas fluid intelligence tends to decrease with age (Horn, Donaldson, ; Engstrom, 1981; Salthouse, 2004).
Other researchers have proposed even more types of intelligences. L. L. Thurstone (1938) proposed that there were seven clusters of primary mental abilities, made up of word fluency, verbal comprehension, spatial ability, perceptual speed, numerical ability, inductive reasoning, and memory. But even these dimensions tend to be at least somewhat correlated, showing again the importance of g.
One advocate of the idea of multiple intelligences is the psychologist Robert Sternberg. Sternberg has proposed a triarchic (three-part) theory of intelligence that proposes that people may display more or less analytical intelligence, creative intelligence, and practical intelligence. Sternberg (1985, 2003) argued that traditional intelligence tests assess analytical intelligence, the ability to answer problems with a single right answer, but that they do not well assess creativity (the ability to adapt to new situations and create new ideas) or practicality (e.g., the ability to write good memos or to effectively delegate responsibility).
As Sternberg proposed, research has found that creativity is not highly correlated with analytical intelligence (Furnham ; Bachtiar, 2008), and exceptionally creative scientists, artists, mathematicians, and engineers do not score higher on intelligence than do their less creative peers (Simonton, 2000). Furthermore, the brain areas that are associated with convergent thinking, thinking that is directed toward finding the correct answer to a given problem, are different from those associated with divergent thinking, the ability to generate many different ideas for or solutions to a single problem (Tarasova, Volf, ; Razoumnikova, 2010). On the other hand, being creative often takes some of the basic abilities measured by g, including the abilities to learn from experience, to remember information, and to think abstractly (Bink ; Marsh, 2000).
Intelligence is challenging to study, in part because it can be defined and measured in different ways. Most definitions of intelligence include the ability to learn from experiences and adapt to changing environments. Elements of intelligence include the ability to reason, plan, solve problems, think abstractly, and understand complex ideas. Many studies rely on a measure of intelligence called the intelligence quotient (IQ).
Intelligence quotients, or IQ tests, compare your performance with other people your age who take the same test. These tests don’t measure all kinds of intelligence, however. For example, such tests can’t identify differences in social intelligence, the expertise people bring to their interactions with others. There are also generational differences in the population as a whole. Better nutrition, more education and other factors have resulted in IQ improvements for each generation.
According to Peter Taylor in The Birth of Project Intelligence, Intelligence is described as a general ability, this ability can be broken down into 6 separate abilities: Adaptability to a new environment or to changes in the current environment, Capacity for knowledge and the ability to acquire it, Capacity for reason and abstract thought, Ability to comprehend relationships, Ability to evaluate and judge, Capacity for original and productive thought.
At least two major “consensus” definitions of intelligence have been proposed. First, from “Intelligence: Knowns and Unknowns” a report of a task force convened by the American Psychological Association:
Individuals differ from one another in their ability to understand complex ideas, to adapt effectively to the environment, to learn from experience, to engage in various forms of reasoning, to overcome obstacles by taking thought. Although these individual differences can be substantial, they are never entirely consistent: a given person’s intellectual performance will vary on different occasions, in different domains, as judged by different criteria. Concepts of “intelligence” are attempts to clarify and organize this complex set of phenomena.
A second definition of intelligence comes from “Mainstream Science on Intelligence”, which was signed by 52 intelligence researchers in 1994:
a very general mental capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience. It is not merely book learning, a narrow academic skill, or test-taking smarts. Rather, it reflects a broader and deeper capability for comprehending our surroundings—”catching on”, “making sense” of things, or “figuring out” what to do. (reprinted in Gottfredson, 1997, p. 13)
FACTORS INFLUENCING INTELLIGENCE
Intelligence has both genetic and environmental causes, and these have been systematically studied through a large number of twin and adoption studies (Neisser et al., 1996; Plomin, DeFries, Craig, ; McGuffin, 2003). These studies have found that between 40% and 80% of the variability in IQ is due to genetics, meaning that overall genetics plays a bigger role than does environment in creating IQ differences among individuals (Plomin ; Spinath, 2004). The IQs of identical twins correlate very highly (r = .86), much higher than do the scores of fraternal twins who are less genetically similar (r = .60). And the correlations between the IQs of parents and their biological children (r = .42) is significantly greater than the correlation between parents and adopted children (r = .19). The role of genetics gets stronger as children get older. The intelligence of very young children (less than 3 years old) does not predict adult intelligence, but by age 7 it does, and IQ scores remain very stable in adulthood (Deary, Whiteman, Starr, Whalley, ; Fox, 2004).
But there is also evidence for the role of nurture, indicating that individuals are not born with fixed, unchangeable levels of intelligence. Twins raised together in the same home have more similar IQs than do twins who are raised in different homes, and fraternal twins have more similar IQs than do not twin siblings, which is likely due to the fact that they are treated more similarly than are siblings.
The fact that intelligence becomes more stable as we get older provides evidence that early environmental experiences matter more than later ones. Environmental factors also explain a greater proportion of the variance in intelligence for children from lower-class households than they do for children from upper-class households (Turkheimer, Haley, Waldron, D’Onofrio, ; Gottesman, 2003). This is because most upper-class households tend to provide a safe, nutritious, and supporting environment for children, whereas these factors are more variable in lower-class households.
Social and economic deprivation can adversely affect IQ. Children from households in poverty have lower IQs than do children from households with more resources even when other factors such as education, race, and parenting are controlled (Brooks-Gunn ; Duncan, 1997). Poverty may lead to diets that are undernourishing or lacking in appropriate vitamins, and poor children may also be more likely to be exposed to toxins such as lead in drinking water, dust, or paint chips (Bellinger ; Needleman, 2003). Both of these factors can slow brain development and reduce intelligence.
If impoverished environments can harm intelligence, we might wonder whether enriched environments can improve it. Government-funded after-school programs such as Head Start are designed to help children learn. Research has found that attending such programs may increase intelligence for a short time, but these increases rarely last after the programs end (McLoyd, 1998; Perkins ; Grotzer, 1997). But other studies suggest that Head Start and similar programs may improve emotional intelligence and reduce the likelihood that children will drop out of school or be held back a grade (Reynolds, Temple, Robertson, ; Mann 2001).
Intelligence is improved by education; the number of years a person has spent in school correlates at about r = .6 with IQ (Ceci, 1991). In part this correlation may be due to the fact that people with higher IQ scores enjoy taking classes more than people with low IQ scores, and they thus are more likely to stay in school. But education also has a causal effect on IQ. Comparisons between children who are almost exactly the same age but who just do or just do not make a deadline for entering school in a given school year show that those who enter school a year earlier have higher IQ than those who have to wait until the next year to begin school (Baltes ; Reinert, 1969; Ceci ; Williams, 1997). Children’s IQs tend to drop significantly during summer vacations (Huttenlocher, Levine, ; Vevea, 1998), a finding that suggests that a longer school year, as is used in Europe and East Asia, is beneficial.
It is important to remember that the relative roles of nature and nurture can never be completely separated. Both of them play integral roles in the forming of ones’ intelligent quotient and thus raises the question on whether the “vs” in nature and nurture is truly a pre-requisite.
INFLUENCE OF GENETICS ON INTELLIGENCE
Many researchers have studied how our intellectual abilities are affected by genetics. Most believe that a large number of genes each play a small role in our intellectual abilities, but it is difficult to isolate and identify these genes. A new study, published in Nature Genetics, involving 80, 000 people have identified a number of genes which contribute to an individual’s intelligence. Researchers have conducted many studies to look for genes that influence intelligence. Many of these studies have focused on similarities and differences in IQ within families, particularly looking at adopted children and twins. These studies suggest that genetic factors underlie about 50 percent of the difference in intelligence among individuals. Researchers have found 69 genes that correlate with higher education attainment—three of those have direct relationship with Cognitive Abilities.
Studies of twins have confirmed genetics basis for intelligence, personality and other aspects of behavior. Twin studies suggest that identical twins IQ’s are more similar than those of fraternal twins (Plomin & Spinath, 2004). Siblings reared together in the same home have IQ’s that are more similar than those of adopted children raised together in the same environment (McGue ; others, 1993). In addition to inherited characteristics, other biological factors such as maternal age, prenatal exposure to harmful substances and prenatal malnutrition may also influence intelligence.