Knows that a group of things changes in quantity when something is added or taken away.
Observe whether the child: knows that a group of things changes in quantity when something is added or taken away.
What it looks like
Three ways this behaviour shows up as a child grows. Each level includes everyday moments to watch for.
Emerging
Just starting
Sometimes reacts to adding/taking away (especially with preferred items) but responses are inconsistent and may be driven by emotion rather than quantity awareness.
What you might see
When one block is added to a small pile, the child does not look back at the pile or change what they do.
When an adult removes one item from a group, the child continues as if nothing has changed and does not search for the missing item.
If offered ‘one more’ snack item, the child shows no sign of noticing the difference between one and two items.
Protests when a favourite item is taken away but does not show similar awareness with neutral items (e.g., blocks).
Smiles or gets excited when an extra item is added but cannot maintain attention to the set long enough to compare before/after.
Uses ‘more!’ after an item is added, but also says ‘more!’ even when nothing has changed.
Expected
On track
In supported play, shows awareness that adding makes ‘more’ and taking away makes ‘less’ for small sets, often using gestures or simple words.
What you might see
Watches an adult add one toy and then reaches toward the bigger group, showing interest in the increased set.
When an adult takes one biscuit away, the child points to the plate and gestures toward themselves as if indicating there is less/they want it back.
During tidy-up, notices when one item is removed from a small group and looks around for it.
Exceeding
Going further
Consistently shows understanding that quantity changes with addition/removal across everyday contexts (snack, toys, sharing), and anticipates the change.
What you might see
Says or gestures ‘more’ when an item is added and ‘gone’/‘no’ when one is taken away, consistently across different activities.
When sharing, notices that if one person takes an item, there are fewer left and may move closer or request another.
After adding one object to a set, the child checks the set (looks back at it) and behaves as if there is now a larger amount.
Predicts a change (e.g., moves hand to guard the group when someone is about to take one away, or smiles when an adult says ‘I’m adding one’).
Uses counting words or touches items to check the new amount after something is added or removed (even if counting is not fully accurate).
Explains the change in simple terms (e.g., ‘more now’ / ‘one gone’) and may direct an adult (‘put it back!’).
Try this at home
Small everyday moments where you can notice this behaviour without setting up anything special.
Snack time: Put 2 crackers on a plate, then add 1 more—notice whether your child reacts as if there are ‘more’ now (points, smiles, says ‘more’).
Play: Build a small tower of 2–3 blocks, then remove one—observe whether your child notices the change and tries to replace the missing block.
Tidy-up: Put 3 soft toys in a box, then secretly take 1 out—watch whether your child looks for the missing toy when they next check the box.
Bath time: Start with 2 bath cups, then offer a third—see if your child changes their language/behaviour (e.g., ‘more cups!’ or distributes differently).
Sharing/turn-taking: Place a few pieces of fruit on a plate and take one away for yourself—notice if your child responds to the reduced amount.
Connected behaviours
Behaviours that scaffold, follow, or co-emerge with this one.
The framework source and supporting developmental research.
Framework source
Development Matters in the EYFS (2012), Mathematics: Numbers (16-26 months).
This construct is a framework-native indicator for early quantitative reasoning about sets changing under simple transformations.
Developmental research
Gelman, R., & Gallistel, C. R. (1978). The Child's Understanding of Number. Cambridge, MA: Harvard University Press.
Understanding number as a property of sets that changes with addition/removal aligns with early counting principles and the developing link between number words and set size.
Five-level rubric (detailed)ShowHide
The full progression underlying the three levels above. Used by the platform’s reasoning agent when planning activities and observations.
Not Yet
Does not notice or respond when items are added to or removed from a small group; treats the set as “the same” or shows no change in behaviour.
When one block is added to a small pile, the child does not look back at the pile or change what they do.
When an adult removes one item from a group, the child continues as if nothing has changed and does not search for the missing item.
If offered ‘one more’ snack item, the child shows no sign of noticing the difference between one and two items.
Emerging
Sometimes reacts to adding/taking away (especially with preferred items) but responses are inconsistent and may be driven by emotion rather than quantity awareness.
Protests when a favourite item is taken away but does not show similar awareness with neutral items (e.g., blocks).
Smiles or gets excited when an extra item is added but cannot maintain attention to the set long enough to compare before/after.
Uses ‘more!’ after an item is added, but also says ‘more!’ even when nothing has changed.
Developing
In supported play, shows awareness that adding makes ‘more’ and taking away makes ‘less’ for small sets, often using gestures or simple words.
Watches an adult add one toy and then reaches toward the bigger group, showing interest in the increased set.
When an adult takes one biscuit away, the child points to the plate and gestures toward themselves as if indicating there is less/they want it back.
During tidy-up, notices when one item is removed from a small group and looks around for it.
Secure
Consistently shows understanding that quantity changes with addition/removal across everyday contexts (snack, toys, sharing), and anticipates the change.
Says or gestures ‘more’ when an item is added and ‘gone’/‘no’ when one is taken away, consistently across different activities.
When sharing, notices that if one person takes an item, there are fewer left and may move closer or request another.
After adding one object to a set, the child checks the set (looks back at it) and behaves as if there is now a larger amount.
Reflexive
Applies this understanding flexibly (e.g., predicts outcomes, checks by counting or matching) and may explain to others that adding increases and taking away decreases.
Predicts a change (e.g., moves hand to guard the group when someone is about to take one away, or smiles when an adult says ‘I’m adding one’).
Uses counting words or touches items to check the new amount after something is added or removed (even if counting is not fully accurate).
Explains the change in simple terms (e.g., ‘more now’ / ‘one gone’) and may direct an adult (‘put it back!’).
