Intelligence – Extremes and Influence

RG 11c

Extremes of Intelligence

A valid intelligence test divides two groups of people into two extremes. The mentally retarded (IQ

70) and individuals with high intelligence (IQ 135) are significantly different.

Intellectual Disability(formerly Mental Retardation)

Mental retardation – having significantly below-average intellectual functioning and limitations in at least two areas of adaptive functioning

●self direction●health and safety●academics●leisure and work

Adaptive functioning includes…●communication skills●self-care●ability to live independently●social skills●community involvement

Intellectual Disability

Cure – none, yet some preventative measures for certain types of MR…●test performed on newborns tests for hidden genetic

disorder called PKU…if detected early, the MR associated with PKU can be prevented by a special diet

●more generally…genetic counseling, pregnancy careservices and education of new parents are otherpreventative strategies

Causes – various factors…●genetics (down syndrome)●environmental (fas, sbs)●deprivation or neglect●no apparent/known cause

Intellectual DisabilityLevels of ID/MR…Mild (50-70) – 85% of all MR – academic abilities at approx. 6th grade level…can learn to live on own and hold a job

Moderate (35-49) – academic abilities approx. 2nd grade level – can be trained in self-care and acquire some reading/writing skills, yet need some supervision

Severe (20-34) – mental capacity of approximately a 5-year-old – learn to talk in most cases and perform simple tasks, yet need close supervision

Profound (below 20) – mental age less than 3 – very limited communication and require constant supervision…usually have numerous physical disabilities as well

Intellectually GiftedIntellectually gifted – have IQ scores above 130-135

Most extensive research on “giftedness” was done by Terman...resulting data much of what we know about subject

●studied 1528 students near top of IQrange into adulthood

●found that gifted children excelled inschool, had overall good health, weregenerally happy (newer researchsuggests that highly gifted children maybe susceptible to certain physical or psychological disorders)

●most continued on path of success, yetmost led ordinary, undistinguished lives

Genetic and Environmental Influences on Intelligence

No other topic in psychology is so passionately followed as the one that asks the question, “Is

intelligence due to genetics or the environment?”

Genetic InfluencesStudies of twins, family members and adopted

children together support the idea that there is a significant genetic contribution to intelligence.

Genetic InfluencesStudies of twins have pointed toward genetic influences…●Minnesota Twins Project – U of Minn – James BouchardoFocused on identical twins reared-apartoIn 1979, Bouchard came across an account of a pair of twins (Jim

Springer and Jim Lewis) who had been separated from birth and were reunited at age 39. "The twins," Bouchard later wrote, "were found to have married women named Linda, divorced, and married the second time to women named Betty. One named his son James Allan, the other named his son James Alan, and both named their pet dogs Toy."

oResearch still ongoing…studied over 100 pairs of identicals separated at birth…all with similar results, much of personality, temperament, intelligence, etc. the same or very similar

Genetic InfluencesOther research supporting genetic influences…●Studies of identical twins have shown a stronger

correlation in IQ scores when compared with fraternaltwins

●adopted children tend to have a more similar IQ to theirbiological parents, rather than adoptive parents

●research coming out of Human Genome Project has alsosuggested that intelligence has a genetic componentscientists point out that a genetic basis of intelligence iscomplex however because it involves the interaction ofmany genes

Environmental Influences

Studies of twins and adopted children also show:

●Greater similarity in IQ scores of those individuals reared together than those reared apart…

Questions on twin studies and intelligenceIf genetic factors play an important role in development of intelligence as measured by an IQ test, then which of the following statements is most likely to be true?    A.  The IQ scores of parents and their offspring will be more nearly     alike than IQ scores of identical twins.    B.  The IQ scores of siblings reared together will be more nearly alike     than IQ scores of identical twins.    C.  The IQ scores of fraternal twins reared together will be more nearly alike     than the IQ scores of identical twins reared apart.    D.  The IQ scores of fraternal twins will be equivalent in similarity to     the IQ scores of identical twins.    E.  The IQ scores of identical twins reared apart will be more nearly     alike than the IQ scores of fraternal twins reared together.

Cont'd...

Jim and Tim are identical (monozygotic) twins that were reared together.  Scott and Michael are fraternal (dizygotic) twins that were reared together.  Given the results of heritability studies of intelligence, which of the following outcomes are most likely to emerge?    A.  Jim and Tim will have very similar IQ's.    B.  Scott and Michael will have very similar IQ's.    C.  Both pairs will have very similar IQ's.    D.  Neither pair will have similar IQ's.    E.  Jim and Michael will have similar IQ's.  

Schooling Effects

Schooling is an intervention that pays dividends, reflected in intelligence scores. Increased schooling

is related to higher intelligence scores.

To increase readiness for schoolworkProjects like Head Start facilitate

leaning.

Reasons for Why Environment Affects Intelligence

1.The races are remarkably alike genetically.

2.Race is a social category.

3.Asian students outperform North American students on math achievement and aptitude tests.

4.Today’s better prepared populations would outperform populations of the 1930s on intelligence tests.

5.White and black infants tend to score equally well on tests predicting future intelligence.

6.In different eras, different ethnic groups have experienced periods of remarkable achievement.

Controversy…Studies have been done comparing different ethnicities, social classes and adopted children, trying to prove impact of genetics or environment on the scores of these different groups●No solid evidence has come about either way…some

evidence suggests that environmental changes caninfluence IQ scores of children in “deprived situations”

●Studies also show that there areprobably test biases for childrenof lower socioeconomic andminority groups due to the normsof most IQ tests being based on scoresof middle-class white children

Genie Wiley

Heritability

Heritability – the amount of trait variation within a group that can be attributed to genetic differences

●HERITABILITY AND HEREDITY ARE NOT THESAME…heritability is looking at differences ingroups where heredity is looking at an individual’straits

●You can only speak of heritable differences withina group of individuals who have shared the sameenvironment