Ilene,
There is a definite psychodevelopmental stage that occurs from about 18 to 24
months of life.  It is called "rapproachment", and is a consolidation of the
child's new skills.  During rapproachment, the child has an intense need for
maternal support and contact.  In other words, the toddler becomes like a baby
again emotionally, just before taking the steps toward true emotional
independence at around 2.  The challenge for mom is to meet these dependency
needs without discouraging growth and independence.  Basically, she needs to
meet dependency needs without punishing attempts to grow away from her.  This
is why the child can be adamant about picking their own clothes and putting
them on unaided, and 10 seconds later insist on being carried.  If moms
realize that this is normal behavior, they are able to meet these needs more
readily than if they consider it a regression.  I look at it as a sort of
review of infancy, toddler style, before going on to the next lesson in
growing up.  Any recent text on developmental psychology will be able to
explain this better, I'm sure.
Catherine Watson Genna, IBCLC