Related abilities
Enjoys playful interactions with others (such as peek-a-boo)
Is able to lift head forward when being pulled to sitting, from lying on back
Enjoys various types of movement, such as being gently swung (4-6 months)
Is usually happy when not hungry or tired (4-6 months)
Is not upset with everyday sounds (4-6 months)
Does not demonstrate frequent or long bouts of being upset (4-6 months)