Do you have the experience of taking music lessons against your wishes? Perhaps you have complained about it because you thought it took you much playtime. But now you'd better thank your parents for their time and money spent on your musical training. A recent study suggests music lessons can make children have better memories than their peers  . The Canadian study showed that after one year of musical training, children did better on a memory test than those who didn't take music lessons. The researchers made the children aged between 4 and 6 into two groups -- one group of children took music lessons outside school, and the other didn't take any musical training. In one year, they took four tests in different times. The results showed brain development changes at least every four months. The children taking music lessons not only did better in musical listening but also made faster progress in other ways, such as reading, writing, math and IQ. People say music is the good medicine for a broken heart. Now it seems music can also help us to improve our memories. We are sure to find more and more in the wonderful world of music. The Canadian study showed that brain development changes  _  .
once a week at least every four months four times a year twice a year