根据短文内容，用方框中所给单词的适当形式填空，每词限用一次。
Have you ever ____ that some people can’t read or write ____ they usually have better memories? This is because they cannot read or write and they have to remember things; they cannot write them down in a little ____. They must remember dates, names, songs and ____; so their memories are being exercised the whole time.
So if you want a good memory, learn from these people: ____ remembering.