Forget expensive educational DVDs and private tutors, the secret to smart children could

be so simple as giving birth【M1】______ to them two years apart. Researchers who studied thousands of children found two-year gap to be optimum in boosting brain【M2】______ power. Any shorter, and the reading and maths skills of the older child dipped. The effect was strongest between the first and second-born, but siblings in bigger families are also【M3】______ benefited. The theory comes from Kasey Buckles, an economist whose own children are, rather unfortunately, just over two years【M4】______ apart in age. She said it is likely that the difference in academic achievement is linked to the time and resources parents can invest in a child before a young sibling arrives.【M5】______ However, waiting for more than two years did not increase【M6】______ the advantage, the Journal of Human Resources will report. Siblings with a two-year spacing include Albert Einstein and sister Maja, and Lord Attenborough and younger brother David. Kasey Buckles, who lead the study told the Sunday【M7】______ Times: "We believe this is the first time anyone has established a casual benefit to increase the spacing between siblings." The study also showed that gaps between children in larger families was also beneficial. Buckles told the newspaper: "The【M8】______ two year gap is significant because the early years are the most important in a childs development so dividing your time when the child is one is more harmful than dividing it when the child is already at school." The effect more pronounced in【M9】______ families with lower incomes, as those with less money could【M10】______ spend to compromise for lack of time.

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