A main source for the ages
Evidence-Informed Milestones for Developmental Surveillance Tools
Jennifer M. Zubler, Lisa D. Wiggins, Michelle M. Macias, Toni M. Whitaker, Judith S. Shaw, Jane K. Squires, Julie A. Pajek, Rebecca B. Wolf, Karnesha S. Slaughter, Amber S. Broughton, Krysta L. Gerndt, Bethany J. Mlodoch, Paul H. Lipkin · 2022 · Pediatrics
- Children
- A review of 34 studies and common checklists, not one group of children
- Where
- Studies from many countries (14 of the 24 with age data were from countries where English isn't the main language)
- Ages
- 2 months to 5 years
- How
- Experts reviewed studies and checklists, then placed each milestone at the check-up age by which about 3 in 4 children do it
- What it found
- Places calling a parent "mama" or "dada" at 12 months, and saying 1 or 2 other words at 15 months. These are ages by which about 3 in 4 children have started, rounded up to a check-up age.
- Limits
- Experts' judgement set the ages, and some milestones rest on opinion rather than measured ages. The lists haven't been tested to see whether they help.