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Factors Influencing Intelligence Quotient Journal of Neurology & Stroke Factors Influencing Intelligence Quotient Abstract Short Communication Intelligence quotient is determined by a number of factors which include both genetic as well as non genetic factors. Even though genetic factors play the major role in Volume 1 Issue 4 - 2014 IQ of an individual. Arun Oommen* determining IQ, various other modifiable environmental influences can influence the Keywords Consultant Neurosurgeon, Lakeshore Hospital and Research Centre, India Intelligence quotient; Wilson effect; Flynn effect; Mozart effect *Corresponding author: Arun Oommen, Lakeshore Hospital and Research Centre, NH-47 Bypass, Maradu, Nettoor P.O, Kochi – 682040, Kerala, India, Tel: +91- Abbreviations 9447043033; Email: [email protected] IQ: Intelligence Quotient; WAIS: Wechsler Adult Intelligence Received: April 24, 2014 | Published: August 25, 2014 Scale Introduction Studies of Genius begun in 1921 by Lewis Terman showed declines in IQ as they grew up. Terman recruited school pupils The abbreviation “IQ” comes from the German term based on referrals from teachers, and gave them his Stanford- Intelligent-Quotient, originally coined by psychologist William Binet IQ test. Children with an IQ above 140 by that test were Stern. Intelligence quotient, or IQ, is a score derived from one of included in the study. There were 643 children in the main study several different standardized tests designed to assess relative group. When the students who could be contacted again (503 intelligence. Some of the popular standardized tests include students) were retested at high school age, they were found to the Stanford-Binet Intelligence Scale and the Wechsler Adult have dropped 9 IQ points on average in Stanford-Binet IQ. More Intelligence Scale (WAIS). The Stanford-Binet Intelligence Scale is now in its Fifth points or more. But parents of those children thought that the Edition. It is a cognitive ability and intelligence test that is used than two dozen children dropped by 15 IQ points and six by 25 childrenThe wereparticular still as geneticbright as and ever, environmental or even brighter factors [6]. that to diagnose developmental or cognitive deficiencies in young several aspects of the environment including socioeconomic children. The test measures five weighted factors and consists of are knowledge, quantitative reasoning, visual-spatial processing, statusdetermine and IQeducation have been are difficult correlated to pin with down IQ, scientifically,and it has been but both verbal and nonverbal subtests. The five factors being tested shown that malnutrition can reduce IQ. workingWechsler memory, Adult and Intelligence fluid reasoning Scale [1].(WAIS) is a test designed Evidence of genetic influences in IQ to measure intelligence in adults and older adolescents. Based on standard scoring of the subject’s rank order on the test • Twin studies shows that identical twins IQ’s are more item content with the median score set to 100, and a standard deviation of 15, although not all tests adhere to that assignment • similarSiblings than reared those together of fraternal in the twins same [7]. home have IQ’s that of 15 IQ points to each standard deviation. It is currently in its are more similar than those of adopted children raised IQ tests generally are reliable enough that most people ages fourth edition (WAIS-IV) released in 2008 [2]. Evidencetogether of environmental in the same environment influences [8]. in IQ individuals score very differently when taking the same test at • Identical twins reared apart have IQ’s that are less similar differentten and older times have or whensimilar taking IQ scores more throughout than one kindlife [3]. of IQBut test some at the same age. It has been noted that 25% of assessed individuals Thethan variability identical twinsin cognitive reared in abilitiesthe same environmentamong different [5]. will obtain a 10-point IQ score difference with another IQ battery. individuals is due to the interaction of genetic and environmental factors. Genetics account for around 50% as per many studies between intelligence batteries at the group level the absence and increasing with age. Shared and non-shared environment Even though not all studies indicate significant discrepancies of differences at the individual level cannot be automatically account for 25% and 20%, respectively, the latter 5% being represented by errors in the evaluation of the cognitive abilities. Environment is able to modify genetically determined assumed [4]. Variations in IQ scores are based on an individual’s cognitive abilities, and an enriched environment can improve specific knowledge, vocabulary, expressive language and the performance. However, the role played by genetics and memory skills, visual special abilities, fine motor coordination environment does not remain the same during the entire lifetime. and perceptual skills. Moreover ones emotional anxiety, tension The increase in heritability of IQ with age is presumably due to and unfamiliarity with the testing process can also influence the IQ score [5] Many children in the famous longitudinal Genetic Submit Manuscript | http://medcraveonline.com J Neurol Stroke 2014, 1(4): 00023 Copyright: Factors Influencing Intelligence Quotient 2/5 2014 Oommen genes that somehow predispose people to gain intelligence via is also correlated with brain size in ways that are likely controlled certain environmental factors. People with high IQ genotypes pick stimulating environments and end up with high IQ. When pathways in autism. we’re kids the brain is still growing and developing so there’s by genes [17], although there are of course disturbed neuronal the chance for environment (mental stimulation, nutrition) to Environmental factors affect its development, but by the time we’re adults the brain has We may be genetically predisposed to a certain brain volume, structure and pathways -- a certain level of intelligence set by our biology -- but how much we achieve isn’t based in biology alone. thatpeaked, the heritabilityso environment of IQ increasescan no longer with age.affect (Wilson it very effect)) much The[9]. The type of life we lead also affects intelligence. resultsRonald Wilsonshow that presented the heritability the first clear of IQ and reaches compelling an asymptote evidence at about 0.80 at 18-20 years of age and continuing at that level Researchers often study twins who’ve been separated at birth to understand further the roles nature and nurture play in human intelligence. They theorize that if intelligence is purely biological, well into adulthood. In the aggregate, the studies also confirm identical twins separated at birth should still have equal IQs. But that shared environmental influence decreases across age, twinapproximating sets from aboutfour countries0.10 at 18-20 showed years a linearof age increaseand continuing in the children to seek out more stimulating environments that further that’s not always the case, they find. Genetic effects cause bright heritabilityat that level of into intelligence adulthood from [10]. 41% A recent in childhood large study (9 ofyears) 11,000 to increase IQ. Programs aiming to increase IQ would be most likely 55% in adolescence (12 years) and to 66% in young adulthood to produce long-term IQ gains if they caused children to persist in have shown that training in using one’s working memory may (17 years) [11]. During brain aging, several environmental insults increaseseeking outIQ. cognitivelyBut it is not demanding clear how experiences.long improvements Recent studiespersist rolecan producein order ato neuronal prevent neuronaldamage by damage. inducing These oxidative defense stress and repairand inflammation. processes are Neurons genetically protection determined, and repair and the play presence a crucial of Improvements in nutritional policy have been implicated in functional variants within genes involved in neuronal protection after training stops [18,19]. and repair likely induce age-related inter individual differences in cognitive phenotypes as a consequence of different levels of isworldwide evidence thatincrease providing in IQ a[20]. high Prenatal nutrient and diet early to very nutrition premature are neuronal damage. However there is still so much limitations of babies,linked toparticularly brain structure, males, behavior can help and to reduce intelligence the loss [21]. of Therebrain our current knowledge about the particular genes involved in established. Knowledge is only lacking about which genes are size and IQ often experienced by these babies [22]. Zinc, Iron, determining IQ. The fact that genes have a strong influence is well folate, iodine, B12 and protein deficiency can also result in low that the genetic and environmental components of IQ may not IQ [23-27].The association between breastfeeding and child cognitive beinvolved completely [12]. The independent. increase in Inheritability other words of IQ withsome age proportion suggests effects. Relationship may be confounded by factors associated development is conflicted by studies reporting positive and null genesof genetic favouring influence intelligence may be predisposing environmental people at the to gainsame or time, lose intelligenceand vice versa (relative [13,14]. to others) As stated in certain above, ways. this could be due to with breastfeeding, specifically maternal socioeconomic whetherclass and theIQ [28].offspring One studywas statesbreastfed that orit waswas the not mother’s breastfed IQ Factors that Affect
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