Here is a section the 4th page into my book:
George looked at him sharply, "What'd you take outta that pocket?"
"Ain't a thing in my pocket," Lennie said cleverly.
"I know there ain't. You got it in your hand. What you got in your hand - hidin' it?"
"I ain't got nothin', George. Honest."
The text goes on to declare that Lennie indeed has something in his hand. It is a mouse and he just lied to George about it. This demonstrates childlikeness in that a child will lie to save himself from sure punishment. This also demonstrates childlikeness because Lennie tried to be "clever" and George, the parent in this situation, saw right through it.
Later on the next page, George is testing Lennie about how they are going to act when they go and talk to the boss. After consenting to say nothing, George encourages Lennie like he would a son:
Good boy. That's swell. You say that over two, three times so you sure won't forget it.
This is how children are. They need repetition and praise. George knows how to handle Lennie. He knows Lennie needs each of these for success and Lennie eats it up!