Thinking and learning
How babies and young children start to make sense of objects, other people, numbers and their own thinking.
When they usually start
Each bar shows the ages when most children in the studies started. Children vary a lot. Tap a milestone to read more.
- Finding a hidden toy. Most children: about 6 to 9 months; typical: about 6 to 8 months
- Pulling a cloth to reach a toy. Typical: about 7 months. The spread of ages hasn't been measured yet.
- Copying actions later. Typical: about 9 months. The spread of ages hasn't been measured yet.
- Looking where you look. Typical: about 10 months. The spread of ages hasn't been measured yet.
- Pretend play. Most children: about 8 to 18 months; typical: about 11 to 14 months
- Knowing what "three" means. Typical: about 3½ years. The spread of ages hasn't been measured yet.
- Understanding that people can believe something untrue. Most children: about 3 to 6 years; typical: about 4 to 5 years
Typical age only: studies haven't yet measured how widely the ages spread.
Objects and how the world works
- Finding a hidden toyMost babies start looking for a toy they have just seen you hide at around 6 to 8 months. In a small study that followed babies closely, all of them started between about 6½ and 8½ months.
- Pulling a cloth to reach a toyBabies start pulling a cloth or mat on purpose to bring a toy within reach at around 7 months. Small studies agree, but none has yet measured how late healthy babies can start.
- Noticing when something seems impossibleIn 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.
Understanding other people
- Looking where you lookBabies start following where you look, to find the thing you're looking at, at around 10 months. Before that, many turn the same way as your head without following your eyes.
- Understanding that people can believe something untrueMost children come to understand that someone can believe something that isn't true somewhere between about 3 and 6 years, often around 4 to 5. In five very different countries, about half of 4-year-olds and most 5-year-olds understood it.
- Understanding what people are trying to doLab studies find signs that babies understand what someone is reaching for by about 6 to 9 months. By 18 months, toddlers who watch an adult try and fail to do something will often do it for them.
- Knowing other people like different thingsBy about 18 months, toddlers in a lab study gave an adult the food she liked, even when they preferred a different one. Younger toddlers gave her what they liked themselves. Answering a question about it in words comes later, around age 3.
Numbers
- Knowing what "three" meansChildren learn what "one", "two" and "three" mean one at a time, often months apart. In US studies, children who knew up to "three" were about 3½ on average. Understanding how counting tells you "how many" comes next.
- Telling small amounts apartIn 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.
- Saying numbers in orderMany children start saying the numbers in order soon after they turn 2. In US studies, most 3-year-olds could say the numbers to eight or ten, though saying the numbers comes well before knowing what they mean.
Memory, pretend play and self-control
- Copying actions laterBabies can remember a new action and copy it later. In a lab study, half of 9-month-olds copied actions they had seen the day before, and a newer study found signs of this from 6 months. Copying straight away, like clapping back, is common by about 8 months.
- Pretend playMost babies start simple pretend play, like feeding or rocking a doll or teddy, around their first birthday. In large studies of parents' reports, about half did this by about 11 to 14 months, and 9 in 10 by about 16 months.
- Waiting for something they wantBeing able to wait for something grows a lot between ages 2 and 5. In a large US study, about half of 4½-year-olds waited the full 7 minutes to get a bigger treat.
- Switching to a new ruleSwitching to a new rule in a game is hard for young children. In a card-sorting game, most 3-year-olds kept using the old rule even after being told the new one, and most 5-year-olds could switch.
Researchers have their own name for this area: Cognitive. The sections on this page follow the way studies usually group these skills:
- Objects and how the world works (Physical cognition)
- Understanding other people (Social cognition (theory of mind))
- Numbers (Numerical cognition)
- Memory, pretend play and self-control (Memory, symbolic play and executive function)