The first year of life according to the noted psychologist Erik Erikson, is the "Stage of Trust." The degree to which the child comes to trust the world, other people and him/herself depends on the quality of care received.
If the child has had good and positive experiences during the first year, he/she will emerge feeling that the world is a good and safe place and that people are dependable. If the care which the child has received during the first year has been inadequate, inconsistent and rejecting, the child will develop an attitude of mistrust and become fearful and suspicious of the world in general.
How can the care giver help the infant develop this sense of trust or feeling good about the world? Respond to the baby with smiles, loving and tender handling and language (talk to the baby). Respond to the infant's cries of distress promptly and effectively. An infant cries because he/she needs something.
See that the infant's needs for food, diaper changes and affection are met quickly. Letting the infant "cry it out" only tells the child that no one is there to meet his/her needs. A distressed infant who is picked up quickly will quiet faster than an infant who is left to "cry for a while": before being picked up. (When trying to quiet a distressed infant, hold him/her up to your should so that he/she can look around easily.)
Hold, cuddle and play with the infant. Change his/her position often in the crib. Place the infant in an infant seat and move him/her around through the house with you. This will provide stimulation as the child sees an hears new sights and sounds. Maintain eye contact when feeding the infant.