单选题
The term "g" (general intelligence) represents a
measure of overall cognitive ability across a variety of tests. It's not the
same as IQ but it does tend to correlate. Everyone agrees that "g" tends to run
in families. But is this down to genetics or to environmental
influences? However, no single gene has yet been conclusively linked
to intelligence. Rather it appears to be a case of complex interactions on many
levels between many different genes. Identical twins have exactly the
same genes, while non-identical twins share about half their genes. Another
feature of twins that makes them an ideal choice for studies is that they tend
to be raised in pretty much the same environment. If a particular feature is the
same in identical twins, but not m non-identical twins, then chances are it's
mainly genes that are controlling that feature. So what do the twin
studies show? Well, first degree relatives tend to have "g" correlation of about
0.4-0.5. (Perfect correlation is 1; correlation of 0 means that the two things
in question are totally unrelated). Identical twins have a correlation of 0.85,
while for non-identical twins it's about 0.6. Which suggests that genes play a
very important role, but are not the only factor, since if they were, the
correlation between identical twins would be 1. Identical twins reared
apart are almost as similar in "g" scores as those reared together. Adopted
children and their adoptive parents have a "g" correlation of zero, while
adopted children and their biological parents tend to have the same correlations
as any parent-child pair. So although genes don't seem to be the only thing
affecting intelligence, their effects seem to be constant and apparently not
overridden by environment. Does heritability of intelligence alter
over a lifetime? Remarkably, it appears so. "g" heritability climbs gradually
from 20% in babies to 40% in children, peaking at 60% in adults. Why this should
be is still a matter of speculation. It's been suggested that as our cognitive
abilities become more complex, new genes may come into play that were not needed
when brain functions were less sophisticated. Or individuals may be drawn
towards environments that fit with their genetic makeup, as time goes by and
genetic effects that started out small in childhood build up together during
adulthood.
单选题
All of the following statements about "g" are true EXCEPT______.
A. "g" is to some extent inherited
B. "g" correlates with IQ
C. "g" can be attributed to a single gene
D. "g" is a measure of cognitive ability
【正确答案】
C
【答案解析】
单选题
Identical twins are chosen as the subjects of the study because
A. they have the same genes and live in the same environment
B. they have some genes linked to general intelligence
C. they have the same heritability of intelligence
D. they are alike in everything except for intelligence
【正确答案】
A
【答案解析】
单选题
The studies on twins' general intelligence show that
A. nothing but genes can determine "g"
B. genes play an important role in "g"
C. the correlation between identical twins is 1
D. identical twins are more intelligent
【正确答案】
B
【答案解析】
单选题
It can be inferred from Paragraph 5 that
A. environment plays a more important role in "g" than genes
B. an adopted child can become as clever as the step-parents
C. "g" changes with the living environment
D. parenting has less effect on one's "g" than genes
【正确答案】
D
【答案解析】
单选题
It can be concluded from the passage that______.
A. it is easy to identify what determines our intelligence
B. genes are a more important determinant of "g" than environment