In a population, with a homogeneous environment for every individual,
100% of the variability in IQ found in the population will be based on
This means that variations in the population will be based entirely in
•However, this does not mean that the environmental effect is negligible. If the
environment effect for half of the population changes then heritability value is not
valid. Also the population in a homogeneously poor environment may have an
overall average IQ that is lower than that of population that is in rich environment.
Thus, the environmental effect is important for the overall average IQ of
population but not for the variation found in the population for that trait.
•In order for heritability of IQ to be 100% or any trait to be 100%, natural selection
must have selected for that trait to be variable based on genetic effects.
4. The comparison of major racial groups with regard to their performance on IQ tests
is problematic and potentially why the test results are flawed. Circle the right
•Major racial groups are not genetically well defined
•Larger genetic variability within as compared to between racial groups
•Phenotypical recording techniques are biased (IQ test)
•Environmental effects are not parsed out
•Heritability estimates are incorrect therefore
•But even if they were correct, interpretation, “spending money on social programs
is a waste” is wrong:
•Genes do not have deterministic effects.
•If we know about their effects and if we study how they exert them, then we can
design “environmental” programs to circumvent, augment, improve on their
5. An experimenter decided to test three different mouse strains A(CD1), B(C57BL6),
and C(DBA/2) in 7 different environmental conditions and analyzed the learning
capacity of these mice in these 7 test situations. Explain whether her results
demonstrate the presence and/or absence of genotype x environment interaction.