What age is a shape sorter for? From 1 to about 2½

A shape sorter fits from about 1 to 2 and a half. Babies start dropping the circle in around a year. Real sorting, turning the shape before pushing, showed up at about 22 months in a lab study. The triangle is last. Every month here is a range, and a wide one: a square at 15 months and a square at 22 are both fine.

You've watched the triangle go in sideways six times and come out again. Here is when the turning starts, what to do at the table, and how to tell when the box is too hard or too easy. We sell shape sorters, and this post links one. Keep that in mind.

When do babies start sorting shapes?

Posting, which just means dropping a block through a hole, starts around a year. Sorting, which means matching a shape to its hole on purpose, starts at about 2. In between sits a year of dumping, carrying and jamming, and all of it counts.

The Centers for Disease Control and Prevention (CDC) has no shape-sorter milestone. Its lists do say what the hand does at each age, and a lab study says when the turning starts. Side by side:

The third column is ours. The CDC lines are from its 1-year, 15-month, 18-month and 2-year pages. The CDC's own tips for 1- to 2-year-olds name "shape sorting and simple puzzles" as matching games to play together.

If you are really asking about puzzles, that is a different job for the hand, covered in when do toddlers start doing puzzles. A knob puzzle is flat matching with a handle built in. A sorter asks for more.

The triangle is the hard part

In 2007, Helena Örnkloo and Claes von Hofsten published a study in Developmental Psychology. They gave toddlers aged 14 to 26 months blocks with five kinds of cross-section to post through holes cut to fit them: circular, square, rectangular, egg-shaped and triangular (three different triangles, seven blocks in all). Each block fit one hole, and only if it was turned the right way.

What they watched was the hand on the way there. Did the child turn the block to match the hole before it arrived, or arrive first and then shove?

The children solved it consistently from 22 months, and the successes were the tries where the block was already turned the right way before the hand reached the hole. In the paper's own detail: at 14 and 18 months the answer was shove. At 22 months the children turned most blocks the right way more often than chance would give. The paper could not show it for the square, which fits four ways round so chance is already high, or for the egg shape. At 26 months they did it for every block.

So the toddler jamming the triangle in sideways and getting frustrated is doing the only thing available to them. At 18 months, trial and error is nearly the whole toolkit.

Worth being precise about what this shows. One lab, age groups four months apart, a box built for the study. "From 22 months" means the youngest group that managed it, not a switch that flips on a birthday. It does not prove that sorters teach the skill, and we won't pretend otherwise.

Which shape goes in first?

The same paper gathers up older work on which shapes go in when, which is the ladder most parents are really asking about. We have not read the originals, so take these as reported.

• Circle first. Gesell and Thompson (1934) and Bayley (1969) both put a ball into a round hole at about 12 and a half months. The circle is the easy one because there is no wrong way round.
• The square, months later. Those same scales put a cube into a square hole at about 19 and a half months. Geerts and colleagues (2003) found most 14-month-olds could already do it. Five or six months of disagreement between researchers on a near-identical task tells you how much this varies.
• Triangle last. In unpublished pilot data from Achard and von Hofsten (2000), the triangle went in on 2 percent of tries at 12 months. At 16 months it was 22 percent, at 20 months 60 percent, at 24 months 69 percent. The cylinder was already at 74 percent at 12 months.

Even at 2, then, the triangle failed about a third of the time. A 20-month-old who gets it in roughly two tries in three is doing exactly what 20-month-olds do. The circle has no wrong way round; a lopsided triangle has only one right way, and that difference is most of a year.

The gap between those two shapes is what separates the shelves. For 1 year olds the job is posting and pulling back out, one or two easy holes. For 2 year olds the turning starts, and a fuller set of shapes earns its place.

Five seconds, then hand it over lined up

The same study timed the attempts, and one detail changes what you do at the table. As the paper reports it, at every age four out of five successes came in the first five seconds of a try. The 22-month-olds kept at it for around 16 seconds on average, with little to show for it.

In plain terms: if it hasn't gone in quickly, it isn't going to. The extra pushing is mostly effort, and it usually ends with the block on the floor.

• Hand it over already lined up. Turn the triangle so its point matches the hole, then pass it. Your child still does the posting, which is the part they care about.
• Don't turn it in their hand. Reaching over to rotate the block takes the whole problem away. Reset and pass it again instead.
• Count to five, then rescue. Five seconds of trying is real work. Twenty seconds of jamming is a child heading for tears, and nothing in the data says the twentieth second teaches more than the fifth.
• Leave the wrong hole alone. If the square is being pressed against the circle, your child is finding that out for themselves, and the finding is the point. The moment you say "other one," it becomes yours.

These four habits rest on the timing data plus our own judgment. No study has tested them at home.

What counts as playing with it

Most of what a 1-year-old does with a shape sorter looks nothing like sorting. That is fine. It is all use, and the CDC's own pages name it: taking toys out of a container, copying another child, on its 15-month list, and putting blocks in and out of containers as its 18-month play tip.

• The lid comes off and everything gets dumped. Legitimate. One hand holding the box while the other pulls the lid is real two-handed work; the CDC does not expect it until its 2-year list, so at 1 the dumping itself is the main event. We think the dumping is the most underrated thing the toy does.
• Posting through the open top. A circle dropped through the big gap where the lid used to be still went in somewhere. Let it count.
• Carrying the pieces to another room. Also use. The shapes are good objects on their own, solid and easy to grip.
• One hole, one shape, over and over. If the circle goes in thirty times and nothing else gets touched, your child has found their level and is drilling it. Don't upgrade them.

Which is why the first sorter should be simple. One hole, a circle-only box, or a drawer-style box where the piece goes in and comes straight back out. A twelve-shape sorter at 13 months is a box of eleven wrong answers.

The simple posting toys live on our fine motor skills shelf. Matching shapes to holes starts on the math and logic shelf from around 2.

How to tell it's too hard

Two things look the same from across the room and mean opposite things.

Interest plus frustration is the right level. Your child keeps coming back to the box, gets the circle, fights the square, shouts, and comes back after lunch. Hand the square over lined up and leave the rest alone.

No interest after a week is the tell that it is genuinely too hard. Frustration makes noise. This makes none. The box sits there, the pieces get carried off, the lid gets used as a plate, and nobody tries to post anything. Put it in the closet and bring it back in six weeks.

If your child is well past 2 and a half, never posts anything into anything, and it worries you, ask your pediatrician rather than a blog. Charts make this look tidier than it is, and we would not use a shape sorter as a screening tool.

What this changes at home

Start with one hole, or a circle-only box, at around a year. Add the square when the circle is boring, and the triangle when the square goes in more often than not. Expect the turning-before-pushing step at roughly 2. The more ways a block fits, the sooner it goes in: the cylinder first, then the square and the even-sided triangle, then the rectangle and the egg shape, and a lopsided triangle last.

The sorter you already own is almost certainly fine. The change that matters costs nothing: who does the turning. For the next year that should be your child, wrong angle and all.

For a child who finds a first sorter too easy, our Noah's Ark Sorter ($41.99, labeled 2 years and up) has six animal-shaped holes in the side of the ark, and each animal fits only its own hole.

Frequently asked questions

What age is a shape sorter for?

From about 1 to 2 and a half. At 1 it is a box to dump and post into; the matching starts at about 2, when a child begins to turn the block before pushing. By about 2 and a half most children have a simple sorter down: the 26-month-olds in the 2007 study got four tries in five through the hole and turned every block in advance. Then a many-shape box takes over.

When do babies start sorting shapes?

Posting starts around a year, with the circle. Sorting on purpose, which means turning the shape to fit the hole before the hand arrives, showed up at about 22 months in a 2007 lab study of 14- to 26-month-olds.

Which shape goes in first?

The circle, because it has no wrong way round. Then the square, then the triangle: a square fits four ways round, an even-sided triangle only three, and a lopsided one just one, so each takes more turning before it drops.

Why can't my toddler get the triangle in?

Because the triangle needs the block turned before it reaches the hole, and that skill arrives at about 2. Before that, trial and error is nearly the whole toolkit. Hand it over lined up and let your child do the pushing.

Should I help, and when?

Count to five. If it hasn't gone in by then, reset the block lined up with the hole and pass it back. Don't turn it in their hand, and don't point at the right hole.

Read next: When do toddlers start doing puzzles? A chart by age · Is my 2-year-old's fine motor behind? · What should a first birthday toy do?