Understanding Intelligence and Validity in Psychology

Oct 9, 2024

Lecture on Intelligence and Validity

Class Announcements

  • Current chapter on intelligence will be wrapped up on Tuesday.
  • Next topic: Chapter 12 on developmental psychology.
  • Schedule follows sequential order after Chapter 12.

Review

  • Previous class: Finished discussion on reliability.
  • Current focus: Different types of validity.

Reliability vs. Validity

  • Reliability: Consistency of test results.
  • Validity: Whether the test measures what it claims to measure.

Types of Validity

1. Face Validity

  • Not in the book, important during test creation.
  • Subjective assessment: Does the test look like it measures the right thing?

2. Content Validity

  • Does the test cover the full range of what it is supposed to measure?
  • Example: A cumulative final exam should measure content from all chapters, not just one.

3. Criterion Validity

  • Does the test correlate with real-world outcomes?
  • Examples:
    • Aggression test should correlate with likelihood of imprisonment.
    • IQ tests should correlate with grades.
  • Two subtypes:
    • Concurrent Validity: Correlation with current real-world outcomes.
    • Predictive Validity: Correlation with future real-world outcomes.

4. Construct Validity

  • Controversial, but important in contemporary psychology.
  • Does the test measure the right theoretical construct?
  • Indirect evidence through other types of validity.

IQ Test Validity

  • Focus on criterion validity.
    • Example: IQ and grades have a correlation of ~0.6.
    • IQ and income have a correlation of ~0.3; with wealth, correlation is near zero.

Understanding Correlations

  • Correlation of 0.6: For every standard deviation increase in IQ, a 0.6 increase in GPA (approx. one letter grade).
  • R-squared (coefficient of determination) helps understand shared variance.

Flynn Effect

  • IQ scores have risen by about 30 points over the last century.
  • Suggests a strong environmental influence on IQ.
  • Influences: Nutrition, education, cultural changes.

Cultural Bias in IQ Testing

  • Concerns about cultural bias in verbal items on IQ tests.
  • Efforts made to improve cultural fairness.
  • Raven's Progressive Matrices considered more culture-fair but have improved significantly over time.

Biological Correlates of IQ

  • Neural Efficiency: Speed and resource use when solving problems correlates with IQ.
  • Brain Size: Controversial; some correlation with IQ.
  • Difference in brain structures between genders; similar average IQ.

Heritability of IQ

  • Defined as genetic influence on individual differences.
  • Estimated through twin studies; heritability increases with age.
  • Environmental influence evident from Flynn effect.

Ethnic Group Differences in IQ

  • Documented average differences in IQ scores.
  • Controversy over causes: Genetic vs. environmental factors.
  • Bias in IQ Tests:
    • Predictive Bias: Consistent prediction across groups; not evident in ethnic differences.
    • Outcome Bias: Tests may not measure true potential due to environmental deprivation.

Key Points on Group Differences

  1. Differences are averages; individuals vary widely within groups.
  2. Heritability does not imply group differences are genetic.
  3. Environment can account for differences as large as average differences.
  4. Genetic differences between ethnic groups are small; most variation is within groups.

Conclusion

  • Genetic contribution to group differences remains uncertain.
  • Importance of understanding both genetic and environmental influences on IQ and group differences.