Chunking

People also do not think only in their heads: we turn, point, write, sort and rearrange what is in front of us, and that is part of how we think. A map is a place where you can do both. This part explains chunking, shows how people really use it, and then applies it to the size of a block: how rough a block can be, when to open one into a map of its own, what the parent then shows about what is inside, and when to stop.

What chunking is

You can only pay attention to a handful of things at once. Chunking is how people get past that limit: they group pieces into units, and treat each unit as one item. Nobody says "I am going to cut, sand, assemble, glue, clamp and finish a chair." They say "I am building a chair." The six steps are still there. They are one chunk.

Chess players. In studies going back decades, strong chess players were shown a position from a real game for a few seconds and could rebuild it from memory far better than beginners. Shown the same pieces scattered at random, their advantage mostly disappeared. The usual explanation is that experts do not see twenty-five separate pieces. They see familiar groups: a castled king with its pawns, an attack lined up on one side. A group is one item to remember, and it also suggests what to do next. Experience builds bigger and better chunks, and the chunks are what let the player think quickly about a crowded board.

Climbers. A climber studying a route from the ground does not memorise hundreds of holds. They read it in sequences: a start, a hard move or crux, a rest, a finish. On a long climb the whole route is broken into pitches, each a manageable piece with its own plan, and the climber thinks about the next pitch, not the whole mountain. The chunks tell the climber where to save energy, where to slow down and where to ask for help.

Everyday life. You do the same with a phone number (three groups, not ten digits), a shopping trip ("the bakery run") or a day ("morning shift, lunch, deliveries"). A good chunk fits the question you are asking now. When the question changes, you open the chunk and look inside.

Thinking with what is in front of you

There is a second idea that matters just as much. Thinking does not happen only inside your head. It is situated: it happens in a place, with tools and surroundings you use as you go. And it is embodied: your hands, eyes and movements are part of the process, not just a way to report it.

Tetris. In Tetris, a block falls and you must decide where it fits. You could turn it over in your mind. Studies of players found that they often do something else: they rotate the piece on the screen, look, and rotate again. The turn on screen was faster and more reliable than the turn in the head. The player is not showing off the answer. They are using the screen to find it. Moving what you can see can be easier than imagining it.

Agendas. Writing "dentist, Thursday, 3 pm" frees your attention, because you no longer have to hold it. But a week laid out in rows does more. You can see that Tuesday has three things stacked on the same afternoon, which you would not notice from a list in your head. Planning on an agenda is thinking with a layout.

Paper. Nobody multiplies large numbers purely in their head. They write the numbers one under the other, carry digits and cross out. Writing a list, sketching a room or drawing arrows between names does the same job: the paper holds the pieces, and you reorganise them until the answer shows.

What these have in common is simple. When there is too much to hold, people put it somewhere they can see and handle it, and the seeing and handling is part of the thinking.

A map works this way. You can drag a block to a new place and look at the result. You can draw a line and see what is connected. You can open a block to look inside, then close it again. You do not have to hold the business in your head. You can arrange it in front of you, change it, and see what shows up. And because the picture is shared, the people you work with can handle it too.

These are the app’s own cards with invented figures, shown the way they look on a canvas. Nothing here is calculated live or saved.

Choosing the size of a block

Now apply chunking to the map. Every map is a choice about what to lump together and what to pull apart. A block that is too big hides what you are trying to see. A block that is too small buries you in boxes. There is no correct size, only a useful one for the question you are asking today.

One block, many sizes

"Fulfilment" can be one block. It can also be six: receive the order, pick the materials, build, check, pack, ship. Each of those could be six more. One block answers "what are the main parts of this business?" Six answer "where does an order spend its time?" Thirty answer "who touches the wrapping tape?" The useful question is not "how detailed should the map be?" but "what am I trying to see, and what size of block lets me see it?"

Signs a block may be too big: different people describe it differently, things you know take a long time seem to vanish inside it, and when something goes wrong you cannot say where. Signs it may be too small: the map is harder to read than the business, most blocks carry the same few words in a row, and updating the map feels like more work than the work. These are signs, not rules. A block can look too big and be fine, because you have no question about its inside.

A rough block is a real block

You do not need to know everything before you draw anything. A block with a name and one sentence is valid: "Customer follow-up: we call or email after delivery, when someone remembers." It says the work exists and has no firm shape yet. Both are worth knowing. The map can be uneven, closely drawn where you are worried and rough where it works. An uneven map is not unfinished. It shows where your attention has been. Completeness is not the goal, and an honestly rough map beats one that looks complete because someone filled the blanks with guesses.

Opening a block into its own map

When one block deserves a closer look but you do not want the detail crowding the picture, open it into a child canvas: a separate map for its inside. The parent stays readable and the child holds the detail. A child canvas is its own document, not a folded-up section of the parent and not a live copy of anything. It is also durable: once it exists, moving around the maps never deletes it. Nesting is a way of choosing what to look at, not of ranking what matters.

A parent summarizes its children

A good chunk carries its own summary. When you open a block into a child canvas, the parent does not go blank. It can show what the inside adds up to, so you can think at the top level and still be working from real figures. That is the point of nesting: not just tidiness, but the ability to see what matters at the level you are looking at, and to drop down only when a figure raises a question.

What the parent shows depends on the kind of figure:

• Costs, working effort and other additive figures from the processes inside add up in the parent. Quantities you have set to aggregate ("Sum compatible values" in Advanced metric settings), such as orders per week or units made, roll up the same way.
• Duration and Delay do not simply add. Steps in sequence add, but parallel steps take the longest, so the parent shows the longest path through its child. Part 11 explains why.
• Related business figures you track on the processes inside, such as the volume a process handles or the cost per unit, travel up with it, so the top-level block can sit beside the numbers that tell you whether it matters.
• Gaps stay visible. If a figure inside is missing, invalid or in a different currency, the parent says its total is partial or unknown. It does not quietly show a smaller number.

The roll-up is a snapshot taken when the figures are calculated, not a live link. Saving a child recalculates the parent's figures, and they are marked out of date while that happens. The parent never edits the child. Innovation blocks stay out of these totals.

This is what makes a high-level map useful rather than merely simple. You can look at "Bake" as one block with a cost, an elapsed time and a volume beside it. If one of those figures surprises you, you open the block and see which step it comes from.

When to stop

Stopping is your judgement. Some questions people find useful:

• Would a different answer change anything? If more detail inside this block would not change a question you are asking, it is probably small enough.
• Can you say what goes in and what comes out? If you can, you can usually leave the inside alone for now.
• Is the detail stable? A step that changes every week is hard to keep honest. Keep it as one block until it settles.
• Does the inside belong to someone else's craft? You might let them draw it.
• Could you come back? A block can be opened later, so stopping now is not final.

That last point is the quiet relief of chunking. You are choosing the right size for today, not committing to the finest detail you will ever need.

A worked example

Illustrative only. Maple Street Bakery is an invented small business, not a real one.

Maple Street Bakery has three people and one oven: Dana, who owns it, Léo at the counter and Priya baking. Dana starts with a map of five blocks: Take orders, Mix and shape, Bake, Pack, Deliver. It fits on one screen. She can see the order of work and who does what.

She notices that Bake looks short on the map but fills the whole morning. She might read this as a sign that the block is hiding something. She opens Bake into its own child canvas and draws what she knows: preheat, load trays, bake 25 minutes, cool 20 minutes, box. Now two of the five steps are waiting, and that was invisible when it was a single word. Cooling is why the delivery van leaves later than she expected.

Back on the parent, Bake now carries figures from the inside, using her invented estimates: preheat 15 minutes, loading 10, baking 25, cooling 20, boxing 10. Each step follows the last, so the elapsed time is 80 minutes. Her hands-on time is only about 20 minutes, the loading and the boxing. She might read this as a morning with a lot of waiting and not much work, and that is hers to interpret. She now has both numbers on one block without having drawn a single extra box at the top level.

She does not go further. She does not split "load trays" into racks and liners, because nobody has a question about it. She does not open Take orders, because it is a phone and a notebook and it works. She leaves Mix and shape as one block with a one-line description, noting in its description that flour comes in on Tuesdays and the shelf is usually fine, because that is something she wants to remember rather than something she needs to draw.

Her map is uneven: closely drawn where she was curious, rough where she was not. She says that is how she wants it. If she later wants to understand why special orders run late, she can open Take orders then.

The same choice appears in a steel shop. At Northline Fabrication, an equally invented maker of custom gates and brackets, "Weld" can stay one block until the question is why gates wait. Then it might open into fit-up, tack, weld and grind. It does not need to open any further than the question does.