A、589. B、598. C、985. D、958. C参与该项目的总共有 985 个孩子，答案为C)。

Scientists have long agreed that we humans are a complex combination of our inherited traits and the environments in which we are raised. How the scales tip in one direction or the other, however, is still the subject of much debate.
    To better understand the nature versus nurture question, UC Santa Barbara psychologist John Protzko analyzed an existing study to determine whether and how environmental interventions impacted the intelligence levels of low birth weight children.
    The key finding: Interventions did raise intelligence levels, but not permanently. When the interventions ended, their effects diminished over time in what psychologists describe as ’’the fadeout effect. ’’
    The research is highlighted in the journal Intelligence.
    ’’Certain environmental interventions can raise general intelligence,’’ said Protzko, a postdoctoral scholar in the META(Memory, Emotion, Thought, Awareness) Lab in UCSB’s Department of Psychological & Brain Sciences. ’’It’s not just pushing scores around on a test; it’s deep changes to underlying general intelligence. The fadeout effect, however, applies the same way. ’’Scientists make a distinction between IQ scores, a quantitative measure of intelligence, and general intelligence, which reflects underlying cognitive abilities.
    Protzko reviewed the results of the Infant Health and Development Program involving 985 children, all of whom experienced an intense and cognitively demanding environment during the first three years of their lives. Three main interventions had been employed to ameliorate the negative effects of being born at low birth weight.
    At age 3, the children were given the Stanford-Binet Intelligence Scales as a baseline measure of their intelligence. At ages 5 and 8—at least two years after the interventions had ended—they were again given intelligence tests.
    The results showed that the interventions had raised the children’s general intelligence at age 3. However, by age 5 the increases were no longer evident. According to Protzko, this demonstrates that the fadeout effect applies to general intelligence.
20. What was the key finding of John Protzko?
21. How many children were involved in the Infant Health and Development Program?
22. What did the results of the Infant Health and Development Program show?