Telling small amounts apart
In lab studies, newborns and babies of a few months look longer when a small number of things changes, like two dots becoming three. Researchers disagree about whether babies are noticing the number or just the amount of stuff.
We haven't yet found studies that measured the age when most children start. The sections below say what is known.
How sure are we?
Researchers disagree. Researchers disagree about whether babies are really noticing numbers, and the studies are small. How we know this
What it’s a sign of
Babies may be born with a rough sense of "how many", though what exactly they notice is still debated.
When studies kept the total amount of stuff the same, babies often stopped noticing the change, which suggests they track amount rather than number. A famous study of babies adding one and one wasn't always repeated, though a study pulling together 12 adding studies found a small effect on average.
We don't know the age by which most babies can do this, or what exactly they are noticing.
A classic study on this
Perception of Numerical Invariance in Neonates
Sue E. Antell, Daniel P. Keating · 1983 · Child Development
- Children
- About 40 newborns
- Where
- Not given in the summary we read
- Ages
- Newborns
- How
- Researchers measured how long babies looked at pictures
- What it found
- Newborns seemed to notice a change from two dots to three, but not from four to six.
- Limits
- We have only read the summary.
A classic study on this
Addition and subtraction by human infants
Karen Wynn · 1992 · Nature
- Children
- Not given in the summary we read
- Where
- Not given in the summary we read
- Ages
- 5 months
- How
- Researchers measured how long babies looked at puppet shows
- What it found
- Babies of 5 months looked longer when one puppet plus one more seemed to make one, as if they expected two.
- Limits
- We have only read the summary. Other studies couldn't always repeat it.
A main source for the ages
Large number discrimination in 6-month-old infants
Fei Xu, Elizabeth S. Spelke · 2000 · Cognition
- Children
- Not given in the summary we read
- Where
- Not given in the summary we read
- Ages
- 6 months
- How
- Researchers measured how long babies looked at pictures of dots
- What it found
- Babies of 6 months told 8 dots from 16, but not 8 from 12.
- Limits
- We have only read the summary.
A study that questioned earlier findings
Infants' Discrimination of Number vs. Continuous Extent
Lisa Feigenson, Susan E. Carey, Elizabeth S. Spelke · 2002 · Cognitive Psychology
- Children
- Not given in the summary we read
- Where
- Not given in the summary we read
- Ages
- First year
- How
- Seven lab experiments
- What it found
- When number and total amount were separated, babies reacted to the amount of stuff, not the number of things, including in the adding task.
- Limits
- We have only read the summary.
A study that questioned earlier findings
Can Young Infants Add and Subtract?
Ann Wakeley, Susan Michelle Rivera, Jonas Langer · 2000 · Child Development
- Children
- About 70 babies
- Where
- Not given in the summary we read
- Ages
- 5 months
- How
- Researchers repeated the adding study
- What it found
- The adding result with 5-month-olds didn't come out the same when repeated.
- Limits
- We have only read the summary.
A study that questioned earlier findings
Babies and math: A meta-analysis of infants’ simple arithmetic competence.
Joan Christodoulou, Andrew Lac, David S. Moore · 2017 · Developmental Psychology
- Children
- About 550 babies in 12 studies
- Where
- Not given in the summary we read
- Ages
- First year
- How
- A study that pulled together lots of studies
- What it found
- Across the adding studies, babies did look a little longer at wrong answers on average, but there were signs that studies with clearer results were more likely to be published.
- Limits
- We have only read the summary.
If you’re worried about your child, talk to your child and family health nurse or GP.
Last checked 2 November 2026