Potty Training - Social Readiness
Youngsters require a lot of help during the initial phases of potty training, and they must be willing to reach out to others.
Teach your child to solicit your assistance. Ask her to call when she needs your help with something, and quickly and attentively respond to her requests.
Both the ability and the desire to imitate others will speed potty training.
Because younger siblings like to follow older ones around the house and are motivated to do what they do, younger children are usually trained at earlier ages.
A socially-ready child will usually manage to learn with very little formal training!
Excerpt taken from The Everything Potty Training Book