A main source for the ages
Predicting age of becoming a cardinal principle knower.
David C. Geary, Kristy vanMarle, Felicia W. Chu, Mary K. Hoard, Lara D. Nugent · 2018 · Journal of Educational Psychology
- Children
- About 200 children
- Where
- The United States, mostly from lower-income families
- Ages
- About 3½ to 5 years
- How
- Researchers tested the same children several times as they grew
- What it found
- Half of these children understood how counting tells you how many by about 4¼ years, and 9 in 10 by about 5.
- Limits
- Ages in the text and a table differ slightly and need checking.