They add giggles and wiggles to their repertoire of happy expressions, and even begin to anticipate pleasurable activities. The trick wouldn't work if anyone else tried it. It was a completely emotional response. Language skills begin to develop at around age 3 months. As with smiling, reciprocity is key to making the most of this development.
Anger also emerges during a baby's early months.
She stared at the characters but kept looking at me for reassurance. When they walked away she let out an audible sigh. Like other babies her age, her understanding of the world had become so sophisticated that she feared the introduction of someone new would throw that order off. A baby in the second half of her first year is also keenly aware of who's most important in her life. Now able to crawl and cruise, she deeply desires independence, but still needs that home base of Mom or Dad or other caregivers.