A researcher examines the correlations between identical and fraternal twins' IQ scores in both higher- and lower-SES families. Which of the following pattern of results is she most likely to find?
A) Higher-SES: identical-.85; fraternal-.85.
Lower-SES: identical-.60; fraternal-.60.
B) Higher-SES: identical-.85; fraternal-.60.
Lower-SES: identical-.60; fraternal-.60.
C) Higher-SES: identical-.85; fraternal-.60.
Lower-SES: identical-.85; fraternal-.85
D) Higher-SES: identical-.85; fraternal-.60.
Lower-SES: identical-.85; fraternal-.60.

Question

Quizplus · Accepted Answer

DB) This choice reflects the understanding that genetic factors (as represented by the correlation between identical twins' IQ scores) tend to have a stronger influence on IQ in higher-SES families, where environmental factors are more uniform and less likely to impede cognitive development. The lower correlation among fraternal twins in higher-SES families compared to identical twins indicates the genetic influence on IQ. In lower-SES families, the environmental factors play a more significant role, reducing the difference in correlation between identical and fraternal twins.D) This choice suggests that genetic influences on IQ (as shown by the high correlation among identical twins' scores) are strong regardless of SES, but the environmental influences (which would reduce the correlation among fraternal twins relative to identical twins) are less pronounced in lower-SES families. This could be interpreted as indicating that in lower-SES environments, external factors affect both types of twins similarly, hence the identical correlation for fraternal twins in lower-SES families as in higher-SES families, but with a reduced influence compared to genetic factors.

A Researcher Examines the Correlations Between Identical and Fraternal Twins