PSYCH Lecture 4

Understanding Intelligence

  • Intelligence has been a subject of discussion focusing on different aspects of its definition, measurement, and influences, particularly regarding its origins.

  • Major discussion points include genetic versus environmental influences and individual differences in intelligence.

Questionnaire on Intelligence

  • A brief questionnaire was presented to gauge beliefs about intelligence, specifically whether it is seen as a fixed trait that cannot be changed.

  • Responses may reflect personal beliefs and could affect academic performance.

Historical Perspective: Francis Galton

  • Galton, a cousin of Charles Darwin, was a pioneer in studying intelligence systematically.

  • He examined the family trees of Cambridge University attendees, hypothesizing intelligence is hereditary and runs in families due to genetic efficiency of brain function.

Behavioral Genetics Research

  • Behavioral genetics investigates the relationship between genetic similarity and IQ scores.

  • Different levels of genetic relatedness are compared to understand genetic and environmental influences on IQ.

Unrelated Individuals

  • Unrelated siblings (e.g., adopted siblings) share 0% of their genes but live in the same environment.

  • Correlation in IQ scores among them is measured at 0.3, indicating that shared environment does provide some influence on IQ.

Biological Siblings

  • Biological siblings share 50% of their genes, increasing the correlation in IQ scores to 0.7.

  • Shared genetics and shared environment contribute to the higher correlation in IQ compared to unrelated siblings.

Fraternal Twins

  • Fraternal (dizygotic) twins share 50% of their genetics and are often raised in similar environments.

  • Correlations of IQ scores vary: 0.47 for opposite-sex twins, and 0.62 for same-sex twins, suggesting similar environments play a significant role.

  • Same-sex fraternal twins often receive more similar treatment from parents, affecting their IQ scores positively.

Identical Twins

  • Identical (monozygotic) twins share 100% of their genes and show high correlations in IQ regardless of rearing conditions.

  • Identical twins raised apart have remarkable similarities in IQ scores (correlation of 0.5).

  • When raised together, their correlation reaches as high as 0.86, emphasizing the impact of both genetics and shared environments.

Conclusion on Behavioral Genetics

  • Both genetics and environment significantly influence IQ scores.

  • The heritability coefficient (h²) helps quantify how much of IQ score variance can be attributed to genetics versus environment.

Heritability Coefficient Overview

  • The heritability coefficient varies across contexts; low income children have a heritability coefficient of 0.1, while high income children show 0.72.

  • In low-income settings, both genetics and environment contribute to IQ, whereas high-income families have less environmental variability, leading to a higher heritability coefficient.

Age and Heritability

  • The heritability of IQ increases with age due to shared educational experiences and environments.

  • At younger ages, both environment and genetics impact IQ scores significantly; as age increases, the genetic influence becomes more prevalent.

Cautionary Note on Intelligence

  • Binet, the creator of the first IQ test, warned against viewing intelligence as a fixed trait, highlighting the importance of practice and training in improving cognitive abilities.

  • The Flynn Effect provides evidence of rising IQ scores over time, indicating environmental factors play a role.

Factors Influencing the Flynn Effect

  • Potential causes of the Flynn Effect include:

    • Improved education systems

    • Better nutrition

    • Enhanced parenting strategies.

    • Modern life's focus on analytical and abstract tasks aligns closely with skills evaluated in IQ tests.

Changes in Intelligence Types

  • Crystallized intelligence (accumulated knowledge) and fluid intelligence (problem-solving ability) demonstrate different trends, with fluid intelligence increasing more significantly over 100 years.

Giftedness and Intellectual Disability

  • Giftedness is typically defined as IQ scores 2 standard deviations above the mean (IQ > 130), with only about 2% of the population fitting this description.

  • Intellectual disabilities are operationally defined as IQ scores below 70, but practical functioning in daily life is also considered.

  • The assessment of intellectual disability considers functional skills like conceptual, social, and practical abilities.

The Importance of Beliefs about Intelligence

  • Dweck's research emphasizes how beliefs about whether intelligence is fixed or changeable significantly influences academic performance.

  • Students who believe intelligence can be developed show improved motivation and academic outcomes compared to those who see it as fixed.

Summary of Intelligence Influences

  • Intelligence is affected by both genetic and environmental factors. Findings support that IQ is not purely genetic or environmental, but a blend of both.

  • Environmental factors such as education and socioeconomic status play crucial roles alongside genetic inheritance in shaping IQ.