You just thought that your toddler would grow out of it. Research from the University of Michigan at Ann Arbor indicates that little kids know how to share, but don't want to. Researcher Craig Smith gave 102 wee ones the chance to share their four scratch-and-sniff stickers with others, and found that their behavior indicated awareness of sharing (indicated by their expectation that others would share with them), but that desire overcame their budding altruistic tendencies.

Possible Preaching Angle:

It's a reminder that from the very beginning of life, humans are a bundle of moral and social contradictions. We can know what is right even as a child, but our innate selfishness holds us back from it. We don't need to be taught what's right. We just need the new life that lets us live it.