Study Cites a Link Between Higher I.Q. and Breast-Feeding By REUTERS CHICAGO, May 7 — The longer infants are breast-fed the higher they are likely to score on intelligence tests as adults, a Danish study said today. I.Q. tests administered to more than 3,000 Danes born from 1959 to 1961 showed that being breast-fed for up to nine months conferred a long-lasting intellectual benefit. The study appears in this week's issue of The Journal of the American Medical Association. Those who were breast-fed less than one month as infants scored a mean of 99.4 on an I.Q. test, with progressively higher scores correlating to the longer duration of breast-feeding. Those breast-fed from seven to nine months scored a mean 106 on the test. Those breast-fed longer than nine months showed a dip in mean score, to 104. A score above 100 is more than 50 percent of people achieve; 25 percent score above 110.