题目内容：

Not long ago, people thought babies were not able to learn things until they were five or six months old. Yet doctors in the United States say babies begin learning on their first day of life.

Scientists note that babies are strongly influenced1 by their environment. They say a baby will smile if his mother does something the baby likes. A baby learns to get the best care by smiling to please his mother or other caregivers. This is how babies learn to connect and communicate with other human beings.

A study shows how mothers can influence social development and language skills in their children.

Researchers studied the children from the age of one month to three years. The researchers tried to measure the sensitivity2 of the mothers. The women were considered sensitive if they supported their children's activities and did not get involved unnecessarily. They tested the children for thinking and language development when they were three years old. Also, the researchers observed the women for signs of depression.

The children of depressed3 women did not do as well in tests as the children of women who did not suffer from depression. The children of depressed women did poorly in tests of language skills and understanding what they hear.

1. influence: to affect the way people behave or think

2. sensitivity: the ability to understand other people's feelings

3. depressed: very sad and without hope

These children also were less cooperative and had more problems dealing with other people. The researchers noted that the sensitivity of the mothers was important to the intelligence development of their children.  Children did better when their mothers were caring, even when they suffered from depression.

1.When do babies begin learning according to doctors in the United States? (不多于5个单词)

2.Why do babies smile to please their mothers or other caregivers? (不多于6个单词)

3.In what tests did the children of depressed women do poorly? (不多于 7个单词)

4.What kind of mothers can help children have a better development? (不多于 2个单词)