lecture 2 Flashcards
intelligence 2
genetic and environmental influences
Family Studies
Twin studies
Adoption studies
Heritability
- how much is variation in a trait due to genetic contributions?
Family studies:
* IQs are more similar the more closely related family members are
* Biological siblings reared together have more similar IQs than adopted siblings reared together
Twin studies:
* Correlation of IQ between identical twins vs. fraternal twins
Identical twins (100% same genes) have higher IQ correlation than fraternal twins (50% genes shared).
Adoption studies:
* Extremely deprived environments gain IQ when in enriched environments
* but IQ of adopted child correlates more with IQ of biological parents
Bottom line:
IQ is influenced by genetic + environmental factors
Environmental Influences
* Amount of schooling
* Studies of children with extra year of school
* Summer vacations
* Dropping out
* Early intervention programs – Head Start
* Expectancy effects on teacher’s part
* Poverty
* Cumulative effect
* Lack of proper nutrition
* Exposure to lead
On average, my IQ is 10-15pts higher than my grandparents!
Flynn effect: average
IQ of the population
rises 10-15pts per generation over time because of better nutrition, education and more stimulating environments.
determining heritability
- Heritability Coefficient, H
- An index of the heritability (amount of variation in a trait that is attributable to genetic factors)
- Varies from 0 to 1
- Calculating H for IQ:
H = (r identical twins – r fraternal twins) * 2
H = (.86 - .60) * 2 = .52
This means 52% of IQ variation is due to genetics.
(*estimates across studies vary from .4 to .7)
A moderate contribution of heredity to IQ
-environmental factors also matter
explanations for the flynn effect
- BETTER NUTRITION
Improved nutrition contributes to better brain development and cognitive functioning, particularly in the lower tail of the IQ bell curve (those at the lower end of the spectrum). Nutrition plays a big role in childhood development and long-term cognitive health. - INCREASED TEST SOPHISTICATION
People today are more experienced at taking tests, which helps boost performance.
As testing methods improve, individuals get better at understanding and responding to test formats, which can influence IQ scores. - INCREASED COMPLEXITY OF THE MODERN WORLD
The modern world is filled with complex information that we process daily (e.g., technology, media, work-related tasks).This constant exposure to information may enhance cognitive abilities, making people more adept at problem-solving and abstract thinking. - CHANGES AT HOME, SCHOOLS
smaller families mean more attention per child from parents.
Parents have greater access to resources (education, books, etc.) and can devote more time to their kids’ development.
More time in school: Increased school years and better educational resources also boost IQ by fostering cognitive growth.
Group differences in IQ
Sex differences
1. Overall IQ
There are few or no significant average IQ differences between men and women.
Men tend to show greater variability in overall IQ scores, meaning there are more men at both the high and low ends of the IQ spectrum.
- Cognitive Task Differences
Women tend to excel in:
Verbal tasks (e.g., language skills, reading comprehension)
Arithmetic calculations (especially in childhood)
Emotional intelligence (recognizing and understanding emotions).
Verbal ability may be influenced by estrogen levels, which affect language-related brain functions.
Men tend to excel in:
Spatial ability tasks (e.g., mental rotation, navigation).
Complex mathematical reasoning tasks, especially in higher-level math.
3. Timing of Differences
Some of these cognitive differences (like spatial ability in men and verbal ability in women) emerge more clearly after childhood or adolescence, possibly due to hormonal changes or social influences.
group differences in IQ pt2
U.S. Statistics
African & Hispanic Americans tend to score lower than White Americans on average in IQ tests (Hunt & Carlson, 2007; Lynn, 2006; Neisser et al., 1996).
Asian Americans tend to score higher than White Americans on average (Lynn, 1996; Sue, 1993).
Canadian Statistics
Canadian First Nations people score on average 18 points lower than non-Indigenous people (Vanderpool & Catano, 2008).
why do these differences exist? within IQ?
-Poverty, health, discrimination, and schooling contribute to IQ differences between ethnic groups.
-Limited resources, poor health, and unequal education can negatively impact cognitive development.
-Measurement Factors
Second-language testing and cultural biases can affect IQ scores.
-Tests may not be culturally relevant, and “culture-fair” tests may still favor certain groups.
-Written tests may disadvantage those not familiar with them.
Why Do These Differences Exist?
-Socioeconomic status and cultural differences heavily influence IQ scores.
-Cultural biases in tests can make some groups perform worse, not because of intelligence, but due to unfamiliar content.
Trends Over Time
-IQ gaps between ethnic groups are narrowing due to improved education and resources.
-Variability within groups is greater than between groups, showing individual differences matter more than group averages.
within-group heritability and between-group heritability
Within-Group Heritability
-Within-group heritability refers to the extent to which a trait (e.g., IQ) is influenced by genetic factors within a specific group (e.g., Asian Canadians or women).
-It measures how much of the trait’s variation within the group is due to genetics as opposed to environmental factors.
Group Differences in IQ
-Between-group heritability refers to the extent to which the difference in IQ between groups (e.g., men vs. women) is due to genetic factors.
-It examines whether the differences in IQ between groups (not just within groups) are explained by heredity or environmental factors.
