What changed?

Three families meet for dinner one Saturday evening. There are three children - a brother and sister aged 3 and 6 respectively and another little girl about 1.5. The two girls are more outgoing and enjoy themselves running around, playing with each other and inventing of new games.
The little boy, a shy little thing, stays with either parent closely for the better part of the evning refusing to mingle, hiding his face in the crux of a parent's shoulder, refusing to look at anyone. His parents dont know what to do. They apologize for their son saying he is too shy and he is always like this. At home, of course, he is different. The adults in the room agree that he is very shy and playfully enjoy a laugh. This is not happening for the first time. The families have met many a time before and the little boy's behavior has been consistent. Even when he played with the other girls, he wore a face of reluctance and boredom.
Dinner is served. Conversationally, the mother of the little boy says that he refused to come when he was told they were going to P Auntie's place for dinner. Even before she completes her sentence, her son starts wailing - continues for about 10 mins. The mother is frustrated and scolds her son with dire results. The crying does not stop. It just gets longer and shriller. Realizing that the boy is not enjoying being the center of attention, the adults divert their attention to the other two kids and change the topic of conversation. Not long after, the boy stops crying.
Dinner is over and dessert is over. A lady in the group sings a wonderful Carnatic song. Everyone appreciates her. There is clapping. The six year old girl bouyed by the enthusiasm and the appreciation volunteers to sing next. An English song. She looks at eveyone as if asking if that is ok. Of course. So what if it is English? Everyone is looking at the six year old waiting for her to sing. She runs numerous tunes through her head trying to figure out what to sing. Her voice is soft and low but she sings beautifully. Praise flows. Claps follow...encouragement and appreciation.
The little boy is watching everyone. There is a visible change in his energy. He no longer is looking shy. He no longer is hiding his face. He joins his sister and sings along with her. His voice is slightly louder and firmer. They sing some lines from Thomas the Tank Engine. The boy continues to sing the same lines over and over again. He knows he does not know the whole song but he is singing. More claps. More praise. More encouragement. More appreciation. More motivation.
It is time to leave. The guests start to leave. Everyone is happy and waving good byes. Including the little boy. He waves his hand. He says good bye. He looks at people straight.
On earlier occasions, the little boy would hide his face in his father's shoulder holding on to him tightly as if he was surrounded by hostile aliens and would have refused to look at anyone. He would refuse to say good byes or talk.
What changed?