B) groups of people differing in age are studied at the same point in time.
C) researchers conduct several cross-sectional or longitudinal investigations.
D) participants are studied repeatedly at different ages, and changes are noted as they
get older.
According to Piaget, 4-year-olds cannot solve a conservation-of-liquid problem because
they
A) focus on the height of the water, failing to realize that changes in width compensate
for the changes in height.
B) do not notice the difference in appearance between the water levels in the two
glasses.
C) have limited experience with the task materials.
D) do not understand the point of the question, “Which glass holds more water?”
Research on ethnic differences in IQ shows that
A) the black”white IQ gap disappears when parental education and income are held
constant.
B) both Hispanic-American and African-American children score, on average, 10 IQ
points below American white children.