Michael's parents have started to worry.
Like any toddler his age, Michael loves to walk on his own and explore the world around him.
He laughs when he is tickled, prefers his fingers over a spoon when eating chocolate pudding, and squeals with delight when the family dog licks his face.
But something seems to be wrong. Michael is 18 months old and has yet to speak a word.
He seems to understand some of the simple things that his parents ask him to do, but he is busy and independent. He cannot stand to be interrupted.
He often ignores his parents when they try to talk to or communicate with him. When they have to redirect what he is doing to bring him to dinner, give him a bath, or put him to bed, he screams -- louder and longer than any of their friends' children.
His parents have reason to be worried.
Beyond causing mischief and getting into everything, there are certain things every toddler should be able to do. The ability to use three to five words other than "mommy" and "daddy" is something that Michael should be able to do.
Is this a cause for concern? Perhaps. But the reasons why Michael isn't speaking can range from minor delays, which will correct themselves over time, to major developmental problems that will last his entire life.
A first step in identifying the cause is to survey a more complete set of Michael's behaviors and compare it to what toddlers should and should not be doing.
At 18 months, Michael should:
respond to his own name
point to things that he is interested in
make and sustain good eye contact with others
follow simple commands
make faces that express his feelings
stack blocks and put simple wood puzzles together
He should not:
sit alone for a long time without seeking someone else's attention
have highly irregular sleep patterns.
For a complete listing of behaviors a toddler should and should not have, check out the Centers for Disease Control and Prevention Web site "Learn the Signs, Act Early"
John Constantino is an associate professor of psychiatry and pediatrics at the Washington University School of Medicine in St.Louis.
Any child who is not reaching these standards by 18 months deserves a good checkup with a child development specialist, someone who can look at and evaluate whether "abnormal" or unexpected behaviors will pass, or are a sign of something more serious.
That checkup should cover six areas of early childhood development:
Emotion regulation or emotional control
A look at the child's living environment: Does it give enough to allow a child to reach his/her developmental potential?
A child's problem in any one of these tested areas could be mild or very serious -- none are "all-or-nothing" categories -- but if even mild problems exist in more than one area (as is all too frequently the case) they can come together to make things worse.
In sizing up these areas of development, experts in child development -- like developmental pediatricians, child neurologists, child psychiatrists and psychologists -- look for ways in which a given child weaves together his or her own abilities, and ways in which he or she uses strengths to make up for any weaknesses.