What is more important than chronological age?

• A. The number of words spoken by age 2
• B. The order of skill development is more important than the chronological age at which each skill is manifested.
• C. The speed of physical growth
• D. The height achieved by age 18

Answer: (B)

Progression of skills follows a relatively stable order, and that sequence is more informative than the exact age at which each skill appears. Developmental milestones are built in a stepwise way: a child typically advances from one stage to the next in a predictable order, even though the timing can vary from child to child. This means you can look at whether a child is moving through the expected sequence rather than fixating on whether they hit a milestone at a specific age.

If a child reaches milestones in the normal order but a bit later, that can still be normal variation; what raises concern is when milestones don’t follow the typical progression or appear in an unusual order. For instance, most children first gain head and trunk control, then sit, then crawl and stand, then walk, and similarly in language—from babbling to saying words to combining words. The emphasis on sequence helps clinicians detect atypical development early and avoids overinterpreting based on age alone.

Measures tied to a single age or a single metric, like how many words are spoken by a certain age or a specific height at a fixed time, can be misleading because they don’t capture the developmental trajectory or the order of skills.