Discuss the evidence for the genetic and environmental contributions to individual intelligence, and explain what psychologists mean by the heritability of intelligence. Genetic contribution to intelligence does exist, yet it does not necessarily predict or determine one’s intelligence. Findings by researchers suggest that that genetics do influence intelligence, but also that it does not do so reliably or completely. Twin researcher Thomas Bouchard estimated that genetics contributes to “about 70 percent” (p 340) to the intelligence test score of any given individual.
He determined this by testing fraternal and identical twins. Identical twin’s scores are almost identical to the scores of the same person taking an intelligence test twice, yet fraternal twin’s scores (who share less genetic make-up than identical twins) are less similar. In addition, the scores of identical twins who were raised separately are still very similar. In addition to genetics, environment also contributes to individual intelligence. Surprisingly, according to geneticists mental similarities between adopted children and their adoptive parents wane with age until the correlation reaches zero by adulthood. p 341) Virtual twins show the same correlation. Throughout life genetic influences become more apparent, but environmental influences do not. Adopted children’s test score slowly begin to coincide with their biological parents’ scores. However, environmental influences are apparent in the intelligence of extremely impoverished children. The results are somewhat generalized, but J. McVicker Hunt determined through very specific studies of impoverished Iranian orphans that lacked care or enrichment had delayed development and lowered intelligence.
Among the poor, biological and genetic influences can be almost negated by environmental influences and lead to cognitive underdevelopment. Heritability can be a tricky concept. “We credit heritability with 50 percent of the variation in intelligence among people being studied. ” (p 343) Heritability refers to a group of people being studied as opposed to individual being tested. If children are raised in identical environments, the varying scores by those children on their individual intelligence tests can only be explained by genetics and heredity (making the heritability 100 percent).
If you were to raise those same children who possess similar heredities in extremely different environments (affluence versus poverty, safety versus abuse, etc) the difference between their individual intelligence test scores would likely vary wildly and, therefore, could be explain by both heredity and environment with a definite influence on the environment. Those children’s heritability would be much lower. Discuss whether intelligence tests are biased, and describe the stereotype threat phenomenon. Give me your opinion about the usefulness (or not) of these tests.
When France passed a law at the turn of the century that all children were required to go to school, it became apparent that some children seemed to be unable to learn under the standard school curriculum presented. Subjective assessments by teachers were untrusted by the government under the belief that their development may have been impeded by inadequate schooling prior to that assessment. Alfred Binet and Theodore Simon based their test on the assumption that all children progress intellectually at the same rate, and that mental age correlates directly with chronological age.
Meaning that a nine year old with the mental age of nine is normal while a nine year old with a mental age of seven or ten will struggle or excel, respectively, with the given curriculum. While Binet intended for his tests to help to improve the education of the individual child, it was later realized that the same test could also work adversely, impeding children’s education and limiting their academic success. This limitation can often result from the stereotype threat which influences test-takers mental perception of whether or not they can perform well in certain instances.
Women, for example, are commonly expected to perform poorly or struggle more on a math exam than men as is the common stereotype. However, when led to believe that they would be able to test as well as males on a given test they generally perform better. Stereotype threat is both self-fulfilling and conveyed by society. This explains why female test takers tend to perform better on math tests when no males test takers or proctors are present. The discussion of whether or not intelligence tests are biased involves iscussing both the scientific definition and the cultural definition. When discussing the cultural definition, bias is present when tests are administered to test takers lacking the ability or experience to answer questions. Intelligence tests measure developed abilities that rely more heavily on previous education or experiences. When discussing the scientific definition of bias, one must consider the test’s validity and whether it predicts future behavior of all test takers or only for certain groups.
If the test only reliably predicted the aptitude of one demographic (men but not women or black but not whites) then the test would be biased and therefore likely contribute to the stereotype threat. In many ways, aptitude and intelligence tests are biased. If the inherent purpose of a test is to draw an intellectual distinction, then bias will most likely present by default. To perform unbiased testing of individuals, one cannot rely on intelligence tests alone.
Intelligence manifests in so many vastly varied forms that to provide a completely accurate test, all factors of intelligence would need to be examined. This would include biological and environmental effects in standard quantitative testing as well as consideration to every individual’s emotional, creative, and practical intelligence, and consideration of mental cognition. Designing and administering such a test would be a monumental task, and I am not sure that it is one that could be accomplished on any practical scale.
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