I've often wondered what a hen thinks upon the arrival of her first egg. Somehow, these girls must know what's going on... just as a woman knows when her first baby is going to arrive.
It's really incredible how they know what the nesting boxes are for; they start laying eggs there right from the start. And, they rarely mess in the nesting box which is a small miracle in and of itself considering the lack of concern for where they drop a load anywhere else!
The entire process, from the formation of the egg to the brooding process to the synchronized hatching of her clutch to mothering her chicks, is truly amazing! The mother hen even communicates with the embryos while in the shell to ensure they develop and hatch at the same time. This communication allows her to know who needs more or less heat to speed up or slow down their development. She'll move those who need more heat to the inside and those who need less to the outside, often making changes several times a day.
After learning all I have about chickens, I must say, I'd be honored to be called a chicken brain. They are interesting, intelligent creatures that don't get the credit they deserve. Give it up to the Mother Hen...