Double consonants are another tricky maneuver. Many toddlers stutter simply because the brain is working faster than the mouth muscles, not because they have a chronic problem. For most children, the powers of language blossom somewhere between 18 months and 2 years, with an outpouring of words flowing together in a crude grammar. Children know an average of about 50 words at this stage. For instance, most 2year-olds will say throw ball, not ball throw.
Twins are particularly interesting because they tend to speak later than singletons.
Dr. Elizabeth Bryan, a British pediatrician who is president of the International Society of Twin Studies, says the delay is probably environmental, not genetic. Children born prematurely often reach milestones later than those born full term, and many twins are premature. Dr. Bryan notes that parents of twins and other multiple-birth children tend to focus their gaze somewhere between the children, inadvertently withholding eye contact, which can be crucial in the development of speech. The new approach to language research relies not so much on such behavioral factors as on brain imaging technology. The studies, which are beginning to localize regions where language defects occur, do not provide clues to treatment.