Grading an activity, one dimension at a time

Making a task harder is not one dial. It is a dozen, and the discipline is moving only one.

The lattice

Any activity can be made harder or easier in a surprising number of independent ways. How wide the base of support is. What the surface is doing. Whether the eyes are open, and what they are looking at. What the hands are allowed to hold. How fast. How long. How much to carry, and how far from the body. How far to reach, and in which direction. What else the person is being asked to think about. What is going on around them. How much help. How much prompting.

Twelve dimensions, each with its own steps, and each moving independently of the others. Experienced clinicians hold most of that in their heads and reach for the right adjustment without enumerating it. Everyone else — and everyone tired, and everyone teaching a student — benefits from it being written down.

Why one at a time

This is the discipline that makes grading useful rather than merely varied.

Suppose someone is standing on firm ground with their eyes open, managing well. You move them to foam and close their eyes, and they struggle. What have you learned?

Almost nothing. The useful question is which of those two things was the problem — because one of them is probably fine and the other is where the work is. Having changed both, there is no way to tell, and the next session starts from the same ignorance.

Move one dimension and the answer is immediate. It is slower, and it is the difference between a progression you can reason about and a sequence of increasingly difficult tasks.

Grading down is not failure

The easier direction gets treated as a fallback, and it should not be.

Finding the step at which someone does something well is usually more informative than finding the step at which they cannot. It establishes a floor, it gives a place to work from, and it produces a session that builds rather than one that consists of repeated near-misses.

A task that is achievable with an obvious next step above it is a better place to be than one that is a struggle throughout, and getting there often means going down two steps before going up one.

The dimensions are not comparable to each other

Any overall “difficulty” number is a rough position, and it is worth being clear why.

Moving from firm ground to foam is one step. Moving from eyes open to eyes closed is one step. They are not the same size of step. They are not the same size of step for two different people, or for the same person on two different days, and the gap between “occasional cues” and “no cues” is something else again.

Within a dimension the steps are ordered but unevenly spaced. Across dimensions there is no common scale at all. So a combined figure is useful for exactly one thing: comparing two setups of the same activity to see roughly which is more demanding. It is not a rating, it does not compare across activities, and it says nothing about a person.

Cognitive load is the one people forget

Of the twelve, the dimension most often left at its easiest setting is what else the person is being asked to think about.

A task performed with full attention in a quiet room is a different task from the same movement performed while holding a conversation, or counting backwards, or deciding where to go next. Almost nothing outside a clinic happens with full attention, which makes this the dimension where the gap between a treatment room and a kitchen is widest.

What this cannot do

It cannot tell you whether a variation is appropriate for anyone. It has no information about a person — there is nowhere to enter any — so it makes no judgement about safety, suitability or indication, and it never will.

What it does is arrange the ways an activity can be varied so that the choice is deliberate and the reasoning is visible. Which variation to use, and whether to use one at all, stays entirely where it belongs.

Frequently asked questions

Why change only one thing at a time?

Because a variation that moves two dimensions produces a result nobody can interpret. If someone struggles on foam with their eyes closed, the useful question is which of those was the problem — and having changed both, there is no way to find out.

Is the overall percentage a difficulty score?

No. It is a position, and it is only meaningful for comparing two setups of the same activity. Moving from firm ground to foam and from eyes open to eyes closed are both one step and are not the same size of step, so the dimensions cannot be added on a common scale.

Which dimension is most often overlooked?

Cognitive load — what else the person is being asked to think about. Almost nothing outside a clinic happens with full attention, which makes it the dimension where a treatment room differs most from real life.

Is grading down a sign of failure?

No, and treating it that way loses information. Finding the step at which something is done well establishes a floor and gives a place to work from. That is usually more useful than finding the step at which it cannot be done.

Does it decide what is safe for a patient?

No, and it cannot. It has no information about anyone and there is nowhere to enter any. It arranges the ways an activity can be varied; every judgement about suitability stays with you.

Can I add my own dimensions?

Not in this version. The twelve cover the ones most commonly used, and any of them can be switched off when not relevant.