Millions of things are present to your senses right now that will never become your experience. When something isn't interesting to you, they don't get your attention. Attention is the mind choosing one thing, in a clear form, and withdrawing from the others.

Where your interest lies puts one object in the foreground and drops the rest. Without that mind's selection, James said, consciousness would be a gray smear.

In a child this is mostly passive. For the duration of whatever their attention is on, the child belongs to the object.

The other objects around them - the toy, the painting kit - were in their space the whole time but they never entered the experience. So when the TV goes off, their "only thing" is gone, which is why their reaction is so strong.