It is only in the cases of failure that she seems to notice the action.

When Mary, greatly interested in what for the moment she is doing, delays her coming, she says, "You ought to come at once, Mary, when I call you, and not make me wait in this way." In the cases when Mary did come at once, she had said nothing.
Mary goes back to her play after the reproof, a little disturbed in mind, at any rate, and perhaps considerably out of humor.
Now Mary may, perhaps, be in time induced to obey more promptly under this management, but she will have no heart in making the improvement, and she will advance reluctantly and slowly, if at all.

But if, at the first time that she comes promptly, and then, after doing the errand, is ready to go back to her play, her mother says, "You left your play and came at once when I called you.

That was right.

It pleases me very much to find that I can depend upon your being so prompt, even when you are at play," Mary will go back to her play pleased and happy; and the tendency of the incident will be to cause her to feel a spontaneous and cordial interest in the principle of prompt obedience in time to come.
Johnny is taking a walk through the fields with his mother.