Many researchers have been interested in whether or not an individual’s birth order has an effect on intelligence. One of the firststudies was carried out in the Netherlands during the early 1970s. ___31___ The test was called the “Raven,” which is similar to theI.Q. test. The researchers found a strong relationship between the birth order of the test takers and their scores on the Raven test.___32___ In 1975, Zajonc and Markus developed the confluence theory to explain the negative effect of birth order on intelligenceinvolving the data from the Dutch. ___33___ However, Rutherford and Sewell in 1991 tested the theory and found no support for it.They concluded that birth order effects did not exist.
         ___34___ On one side there are Zajonc and Markus, who state that birth order effects may be explained solely by family sizeand the spacing of births. With short birth intervals, increasing order of birth will be associated with lower intelligence levels. Butwith long birth intervals, this pattern may be reversed. ___35___ They show that the confluence model does not explain anyrelationship between birth order and intelligence that may exist in the American data. Up to date, there is no agreement between theseopposing views. And such a debate may continue for years to come.
【題組】31.
(A) There are definitely two sides to this issue.
(B) Scores decreased as the family size increased and also with birth order.
(C) An intelligence test was administered to over 350,000 Dutch males when they turned 19 years of age.
(D) On the other side are Rutherford and Sewell, who studied more than 10,000 American high school graduates.
(E) Since then, the theory has been elaborated and even extended to explain the positive effect of birth order on intelligence.