Infants use all their senses to learn the world. They "talk" with (1) ______ others through actions and sounds, experiment with objects and noises. (2) ______ They enjoy watching the results of their actions. This is how children learn, make sense of the world, and learn to communicate. When the (3) ______ babies coo, babble, and interact with others, they are developing language skills. Children quickly begin to understand the meanings of symbols—that a smile and pleasant tone of voice mean the person speak to them is happy, (4) ______ that dimming lights mean it is naptime, and that putting on a coat means a (5) ______ trip to outside. Young children think that when they cannot see to someone and (6) ______ something, it is gone forever. When important people in their lives leave, they do not understand that they will return. This period of development is hard with parents and children. (7) ______ Parents can make these times less stress by letting a child hold and (8) ______ keep personal objects, such as stuffing animals, blankets, or a family (9) ______ photo. Around the second year of life, children begin to form mental pictures of objects, and that makes easier for them to say goodbye to (10) ______ moms, dads, and other people they are about.