Most adults find it hard to remember the things happened while they were children． Now scientists have found exactly when these memories （1）d　　．

    A new study has found that most three﹣year﹣old children can remember a lot of what happened to them a year （2）e　　 ，and these memories are still clear while they are 5 and 6， but by the time they are over 7， these memories become weaker （3）r　　．

    Most children by the age of 8 or 9 can only remember 35% of their （4）e　　 from under the age of 3 according to the new studies．

    The scientists say this is because at around this age the way we form（形成） memories begins to change． They say that before the age of 7 children do not have a （5）s　　 of time and place in their memories． In older children， however， the early things they can remember become more adult﹣like in the way they are formed． Children also have a far faster speed of （6）f　　 than adults． The discoveries also help to explain why children can often have clear memories of what they have done， （7）b　　 then forget them just several years later．

    The children were organized to the laboratory for the first time at the age of 3 and discussed 6 impressed（印象深刻的） things from their past， such as the first relaxing trip with your family，the first （8）d　　 accident you met， and the first day of school． The children then returned for a second （9）s　　 between the ages of 5 and 9 to discuss the same things． The scientists found that between the ages of 5 and 7，the amount（量） of memories that the children could remember （10）r　　 between 63%﹣72%． However， between the ages of 8 to 9， the amount of memories that the children could remember fell to between 35%﹣﹣36%．