When Susan was one-and-one-half years old, she had been playing the “lion game” with her mother for the past few months. With a lion puppet on her hand, Susan's mother made the lion roar, tickle, bite, and tease Susan, who seemed delighted to be aroused and frightened. Susan and her mother first concocted this curious blend of happiness and fear, approach and withdrawal, when they discovered tickling games. Susan was only six months old at the time. As her mother loomed in for the tickle, Susan would pull away, turn her body to the side, and at the same time reach out for her mother, look at her, and laugh heartily with her mouth wide open. From early in the first year, simple games create emotional challenges – such as a conflict between approach and withdrawal – that are negotiated in the long-term parent–infant relationship.

Emotions are good for us, a kind of psychological workout. Joy, fear, surprise, and sadness move us internally, shifting our body chemistry and lighting up our brains. Babies are more emotionally alive than most adults: they feel and respond to everything. As people leave infancy behind, however, they learn not to feel as much or as intensely. People who are repeatedly left alone as children, for instance, experience powerful fear and sadness during the separation. Without someone present to whom a child can turn to relieve them, these emotions had to be suppressed because they would be too overwhelming.