Neuropsychology

Executive Function Task Laboratory

Four executive tasks and six underlying capacities. Predict what each task needs, then take a capacity away and see which tasks notice.

Simulated — original task descriptions and a transparent model, not real testing

Learning objective

By the end you should be able to say why no executive task is pure, and why the lowest score does not name the weakest process.

About 30 minutes, in two experiments. Nothing you do here is saved or sent anywhere.

A transparent model, not a measurement

Nobody performs these tasks. Each task is a set of weights on six capacities, and every score you see is a weighted average computed from sliders you set. The weights are an argument about what tasks require, written for teaching. No standardised test, subtest or item is reproduced, and no score means anything about the person reading it.

Experiment 1. For each task, tick the processes you think it needs, then reveal the model's weights.
Experiment 2. Reduce one capacity at a time and watch all four task scores.
Then find two different reductions that make the same task the lowest.

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1 What each task needs
2 Taking a capacity away

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Key terms

Inhibition, switching, updating: Three processes this model treats as separate capacities you can turn down. They are the model's inputs, not a settled inventory of what the brain does.
Processing speed: How quickly material is dealt with, independently of whichever process a task is named after.
Task weight: How heavily one task draws on one process in this model. It is revealed only after you have committed to a guess.
Strategy: Where the person sits between working quickly and working accurately. It is set separately from any capacity.

The task

Which processes does it need?

When you have done all four

What this task needs, once revealed

The four tasks

The whole weight matrix

No row contains a single non-zero entry, and no row contains fewer than five. There is no pure executive task, and the weights are an argument about task demands rather than a measurement of them.

A fictional report reads: "Performance was below the control range on the colour-word conflict task and within range on the other three executive measures. This indicates a selective impairment of response inhibition."

What is the single most important thing wrong with that sentence? One task is not enough evidence for any conclusion Reduced processing speed produces the same pattern, and the colour-word task is the most speed-loaded of the four It should have said which brain region is responsible Nothing - that is what the colour-word task measures

Every one of these tasks loads on several processes at once, so one low score never identifies which capacity is reduced. That is the task-impurity problem, and it is why a battery reports converging patterns across tasks rather than a diagnosis from any single one. Speed and sustained effort are part of the pattern, not nuisance.

Executive Function Task Laboratory

Learning objective

A transparent model, not a measurement

First, a judgement

The laboratory

Experiment 1 - what each task needs

What this task needs, once revealed

All four tasks, at these capacities

Reading this

The four tasks

Challenge - a report to correct

What this demonstrates