Noticing when something seems impossible
In lab studies, babies from about 3 to 5 months old look longer at scenes that seem impossible, like a screen passing through a hidden box, as if surprised. Researchers still debate what this longer looking means.
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 what babies' longer looking means, and many young babies in these studies don't show it. How we know this
What it’s a sign of
Babies may already have some expectations about how solid objects behave, long before they can tell us.
Some studies found signs of this from about 2½ months, and what babies notice keeps growing through the first year. But at 3½ months only some babies showed it, and a study pulling together 76 looking studies found the effect was real but small, with mixed signs that clearer results were more likely to be published. Critics argue that babies may look longer simply because something is new.
We don't know at what age most babies show this, because studies compare groups rather than following each baby. Most studies are from North America and Western Europe.
A classic study on this
Object permanence in 3½- and 4½-month-old infants.
Renée Baillargeon · 1987 · Developmental Psychology
- Children
- About 90 babies in three groups
- Where
- Illinois, United States
- Ages
- About 3 to 5 months
- How
- Researchers measured how long babies looked at possible and impossible scenes
- What it found
- Babies of 4½ months, and some of 3½ months, looked longer when a screen seemed to pass through a hidden box, as if surprised. At 3½ months only the babies who got used to the scene quickly showed this.
- Limits
- Small groups in one lab. Longer looking may not mean the same thing as understanding.
A classic study on this
Infants’ reasoning about hidden objects: evidence for event‐general and event‐specific expectations
Renée Baillargeon · 2004 · Developmental Science
- Children
- Many studies, mostly small
- Where
- Mostly North America
- Ages
- About 2½ to 12 months
- How
- A review that brings together many looking studies
- What it found
- Some looking studies found signs of this from about 2½ months. What babies notice grows bit by bit through the first year, for different kinds of events.
- Limits
- Most of the studies reviewed come from the author's own research group.
A study that questioned earlier findings
Perceptual and conceptual novelty independently guide infant looking behaviour: a systematic review and meta-analysis
Linette Kunin, Sabrina Hsiao-Ling Piccolo, Rebecca R. Saxe, Shari Liu · 2024 · Nature Human Behaviour
- Children
- About 1,900 babies in 76 studies
- Where
- Mostly North America and Western Europe
- Ages
- 3 to 12 months
- How
- A study that pulled together lots of looking studies
- What it found
- Babies did look a little longer at impossible scenes overall, but the difference was small, and studies of older babies found smaller differences.
- Limits
- Mixed signs that studies with clearer results were more likely to be published. It reports group results, not ages for individual babies.
If you’re worried about your child, talk to your child and family health nurse or GP.
Last checked 2 November 2026