ABSTRACT
This chapter looks at the mystery of why intelligence quotient (IQ) scores are rising; methods of looking at nature versus nurture; social class and IQ; whether vitamins can boost IQ; and whether pollution affects IQ. It also looks at whether we can teach children to be more intelligent; gene–environment interaction; the genetics of genius; and the inheritance of personality traits. If the IQ scores of adopted twins resemble those of their biological parents, that suggests the influence of heredity is higher. If their scores resemble those of their adoptive parents, that suggests the role of the environment is more important. A gene–environment interaction effect occurs when the effect of exposure to an environmental factor depends on the person's genotype. Two different theories claim that individuals should differ in their developmental plasticity and susceptibility to environmental influence: J. Belsky's differential-susceptibility hypothesis and W. T. Boyce and B. J. Ellis's biological-sensitivity-to-context thesis.
