A new study confirms the baby in the family will always be the baby.

Not only that, but the youngest child will most often be perceived as shorter than he or she really is, even by mom.

The study's authors call it the "baby illusion," and they say mothers underestimated the height of their youngest by an average of 3 inches, but they accurately judged the height of any older children they had.

The study just published in the latest issue of Current Biology says it may be an adaptive mechanism, so that moms will nurture and protect the most vulnerable offspring.

The lead researcher says this explains why the baby of the family will always be seen as the baby.

--Rob Archer