Does your child have a nickname?
I always went by my full name--Christina--though people have, since I was a school-age child, insisted on calling me by every variation of my name known to man. Christy, Chrissy, Christine, Chris. I am most regularly mistaken for Christine, which irks me to no end. I have nothing against the name--it's just that it's not my name.
Over my years spent in the classroom however, I've come to realize that many kids go by nicknames. Nicholas goes by Nick, Abagail by Abby, Kathleen by Kate. And because so many children seem to have nick names, adults seem to default to calling kids by the shortest variant of their name--even if the child doesn't go by that name.
It then becomes an uphill battle for the parent that wants to keep their child's name un-truncated---Benjamin instead of Ben, Cassidy instead of Casie. Does your child have a nickname? Did you make that decision consciously, or did your child just start getting called a shorter version of their name once they started school? Do you expect your child to continue using a nickname an adult, or do you think they'll go by their full given name?