Identify the statements that are correct about the influence of heredity on intelligence:
(A) The intelligence of identical twins reared together correlates almost 0.90.
(B) The intelligence of brothers and sisters reared together correlates about 0.65.
(C) The intelligence of identical twins reared in different environments correlates about 0.72.
(D) The intelligence of siblings reared apart correlates about 0.25.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (C) and (D) only
The evidence for hereditary influences on intelligence comes mainly from studies on twins and adopted children: the closer the genetic relation, the higher the correlation between their intelligence.
(A) The intelligence of identical twins reared together correlates almost 0.90. Correct. Identical twins share all their genes and also their environment, so their intelligence correlates almost 0.90, the highest figure.
(B) The intelligence of brothers and sisters reared together correlates about 0.65. Incorrect. Brothers and sisters reared together correlate about 0.50, a little below fraternal twins reared together (almost 0.60). The figure 0.65 in the statement is wrong.
(C) The intelligence of identical twins reared in different environments correlates about 0.72. Correct. Even when separated, identical twins correlate 0.72, which points to a strong hereditary influence.
(D) The intelligence of siblings reared apart correlates about 0.25. Correct. Siblings reared apart correlate about 0.25, much lower than siblings reared together, which shows that environment also matters.
NCERT (2025-26): “Intelligence: Interplay of Nature and Nurture … The evidence for hereditary influences on intelligence comes mainly from studies on twins and adopted children. The intelligence of identical twins reared together correlate almost 0.90. Twins separated early in childhood also show considerable similarity in their intellectual, personality and behavioural characteristics. The intelligence of identical twins reared in different environments correlate 0.72, those of fraternal twins reared together correlate almost 0.60, and those of brothers and sisters reared together correlate about 0.50, while siblings reared apart correlate about 0.25.…” |