Ch 9 Intelligence and IQ TestingGenetic and Environmental Influences Family Studies: Examine the extent to which a trait runs in a family. Twin Studies: Compare correlations in a trait with MZ and DZ twins MZ greater than DZ. Adoption Studies: Examine the extent to which adopted children resemble their adopted or biological parents. Family Studies: Galton’s examination of “intellectual brilliance” Proportion of relatives who achieved greatness decreased with biological distance. IQ correlation for brothers/sister is .5, for cousins .15 Concluded data supported this notion. Genes and environment are usually confound.Twin Studies: These attempt to disentangle the effects of nature vs nurture. Compare two types of twins: Monozygotic (MZ) or Dizygotic (DZ) Answers the question - Which contributes mores, the genes, or the environment? MZ: one egg that splits. 100% identical. DZ: two eggs, 50% identical Higher correlations between MZ twins suggest a strong genetic component. Intelligence Correlations: MZ twins: .7-.8 DZ twins: .3-.4 Adoption Studies: Examines how much children adopted into new homes resemble their adoptive vs. biological parents. Tell Us: Clear environmental influence. Adopted children’s IQ correlate with their adoptive parents IQ’s. Possible Confound: Selective PlacementEnvironmental Influence on IQ Social (eg. Home, school) Biological (eg exposure to toxins, nutrition)Birth Order: Zajonc - controversial claim: later-born children are less intelligent than earlier-born ones. However, within a given family, there is virtually no relationship between birth order and IQ Across families, children with larger families have slightly lower IQs (by a few point) than those who are from smaller families.Schooling: Number of years in school has a moderate correlation with IQ: 0.5-0.6. Early Intervention: Head start program within the 60’s. Short term, but not long lasting increases in IQ Benefits: Less likely to drop out of high school Less likely to be held back a grade. Correlation Expectancy Effects: IQ based teachers expectancies can affect teachers interactions with students. Rosenthal and Johnson told teachers that certain students (randomly picked) would show gains in intelligence over the year as indicated by an IQ test (which was fake) Actually found a slight increase in IQ after 1 years. Extra positive reinforcement and encouragement for those students?Poverty: Social and economic deprivation can adversely affect IQ: Malnutrition, lead exposure, and lack of breast feeding all associated with lower IQ. Effects are cumulative.Fylnn Effect: Average IQ scores have been rising at a rate of approximately 3 points per decade. Potentially the result of unidentified environmental influences: Increase test sophistication Increased complexity of the modern world. Better Nutrition: Smaller families and more years in school.Sex differences in IQ: Controversial findings suggest a small advantage for males (3-5 points) Outliers affect average, pulling it to right. Major studies find no or negligible difference.Sex Differences: Females Better at verbal task (spelling, writing, pronunciation) and tongue twisters. May be related to estrogen levels. Better at adding/subtracting as children. Better at distinguishing emotions on faces. Do not talk more than males. Average 16,000 words a day.Sex Differences: Males Better at task requiring spatial ability. Mental rotation task, geography, etc. Better at more complicated mathematical task (geometrical proofs)Sex differences in IQ: Genetic factors may be implicated in sex differences: Stability across time despite changing gender roles. But the environment and socialization matter. Don’t see differences in spatial ability in infants. Increasing number of women in “hard” sciences Racial Differences in IQ: Avg IQ: Asian Americans > Whites > African Americans > Hispanic Americans. The difference between African Americans and Whites is most studied. 15 pt difference sometimes. Potentially the result of test bias. Variability within races is considerably larger than variability between races. IQ differences between the races are narrowing. Likely due to environmental differences, especially socioeconomic status. Stereotype threat may also play a part. Test Bias: When a test predicts outcomes better in one group than it does in another group. Most IQ test do not appear to have test bias. Correlations between IQ scores and other outcomes are similar across all races. Biased items exist, but may be harder to detect than you think. Bias likely comes from society.Overview: Race cannot be used to determine and individual’s IQ. Group differences in IQ are likely the result of environmental differences between groups as a whole. Intelligence is not clearly defined and measurable concept: it is an array of many other factors.Review: Cattell’s concept of fluid intelligences refers to: Capacity to learn new ways of probelm solving. A single common factor underlying our intelligence (g). Spearmen. Intelligence tied to specific (s)