According to the Centers for Disease Control and Prevention, a baby is considered an infant until he reaches one year of age. During this stage, the infant reaches several developmental milestones.
In the initial stages of development, the infant learns to develop bonds with parents and caregivers. Then, the infant explores his environment as he develops better vision and processes what he sees and hears. As the brain develops and more visual and audio cues are processed, language, memory and reasoning skills are being developed. As the infant gets older, other physical and developmental milestones are reached that lead to the toddler stage of development.