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Determinants of Intelligence - Hereditary Factors

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Topics

Estimated time: 11 minutes
  • Introduction
  • Main Studies and Evidence
  • IQ and Heredity Studies
  • Real-Life Application
  • Key Points: Hereditary Factors
CISCE: Class 12

Introduction

Heredity refers to the genetic transmission of traits - including intelligence - from parents to offspring. Scientists study twins and family members to understand how strongly genes affect intellectual ability versus environmental factors.

CISCE: Class 12

Main Studies and Evidence

Twin Studies:

  • Identical Twins (Monozygotic): Share 100% of genes.
  • Fraternal Twins (Dizygotic): Share 50% of genes.

Key Research:

  • Newman, Freeman & Holzinger (1937): Compared identical twins raised apart; their IQ scores were extremely similar—suggesting genes matter most.
  • Shields (1962): Studied 88 pairs of identical twins (half raised together, half apart). IQ correlations: 0.77 (together), 0.76 (apart); again, genes played a larger role than upbringing.
  • Other studies: Even with environmental changes, IQ usually remains stable after early childhood.
CISCE: Class 12

IQ and Heredity Studies

CISCE: Class 12

Real-Life Application

Imagine baking two cakes using the same recipe but in different ovens. If both taste alike, it's the recipe (genes), not the oven (environment), that’s most important.

CISCE: Class 12

Key Points: Hereditary Factors

  • Heredity refers to the genetic transmission of traits, including intelligence, from parents to children.
  • Twin studies are commonly used to study the role of heredity in intelligence.
  • Identical twins share 100% of genes, while fraternal twins share about 50% of genes.
  • Studies by Newman, Freeman & Holzinger (1937) and Shields (1962) found very similar IQ scores in identical twins.
  • These findings suggest that heredity plays a major role in determining intelligence.
  • Family studies also show that intellectual abilities often run in families.

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