The importance of environment in determining an individual's intelligence can be【C11】______by the case history of the【C12】______twins, Peter arid John. When the twins were three months old, their parents died, and they were placed in【C13】______fostered(寄养的)homes. Peter was【C14】______by parents of low intelligence in an【C15】______community with poor educational opportunities. John,【C16】______, was educated in the home of well to do parents who had been to college. This environmental【C17】______continued until the twins were【C18】______their late teens, when they were given tests to【C19】______their intelligence. John's IQ(智商)was 125, twenty-five points higher than the【C20】______and fully forty points higher than his identical brother.
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