Sustained attention and cortical fatigue: why you perform worse in the second half

One observation repeats across every performance context: decision quality falls over time. It happens in the last quarter of a match, on the final laps of a stint, in the fourth meeting of the day, in the second hour of a precision task. The usual vocabulary for it — lost focus, mental dip, switching off — is descriptive but useless, because it points at nothing trainable.

Take the phenomenon apart and concrete mechanisms appear, degrading at different rates, each of which can be assessed and worked on separately.

Attention isn't one capacity, it's several

Distinct processes live under the label “attention”. Telling them apart matters, because a profile can have one that's excellent and another that's clearly limiting.

• Selective attention: prioritising one stimulus among many. It's a filter, and its quality determines how much irrelevant information reaches deep processing.
• Sustained attention: keeping perceptual performance stable over time. This is what defines the second-half curve.
• Divided attention: splitting resources between two simultaneous demands. It almost always costs performance in at least one.
• Inhibitory control: suppressing an automatic response that would be an error in this context. It's what stops you biting on the feint.
• Attentional flexibility: shifting focus between broad and narrow, near and far, as the situation requires.

The common error is training the sustained kind — longer sessions — when the real deficit is in selective attention or inhibitory control. Extending exposure doesn't fix a filter that lets too much through; it only prolongs the expenditure.

Where the cost comes from

Filtering is expensive. Every irrelevant stimulus that reaches conscious processing and has to be actively discarded consumes resources unavailable to the primary task. That cost isn't perceived stimulus by stimulus: it accumulates.

The first place it's paid is perceptual input, and hence the direct link to everything above: an inefficient oculomotor system generates more movements than necessary, and every unnecessary movement is one more operation to manage. A functionally narrow peripheral field forces you to look at what should be detected without looking. An unstable fixation demands re-reading. All those small overheads come out of the same account.

The second place is executive control: holding the rule active, inhibiting the automatic response, updating the situation model. These operations are the first to degrade under fatigue, and their degradation is especially dangerous because it isn't perceived as tiredness — it's perceived as decisions you wouldn't have made when fresh.

How it shows up in each context

Sport

Reading errors appear before technical errors. The movement is still correct but the wrong option is chosen, or the right one too late. The focus also narrows: context stops being perceived and only what's directly in front gets played.

High-speed contexts

Rep-to-rep consistency deteriorates before the best single result does. Visual reference is lost more often and corrections become larger because they start later.

Cognitive work and professional decision-making

The need to re-read increases, holding several elements in mind becomes harder, and there's a growing tendency to resolve by shortcut or bias rather than analysis. It's the least visible manifestation and the one that produces the most expensive decisions.

What can actually be trained

There are two routes, and they work best combined: reduce the cost per unit of task, and increase the capacity to sustain it.

Route 1: reduce the cost

The most profitable and the most ignored. Anything that improves input efficiency — clean oculomotor control, functional periphery, gaze stability during movement — frees attentional resources without training attention at all. A system needing fewer operations to obtain the same information lasts longer.

Route 2: increase endurance

Here the demand is trained directly, and the key is progressing cognitive load rather than duration. Add rules, switch them mid-series, introduce relevant distractors, require inhibition of automatic responses, and work under the conditions the real context imposes.

1. 01Establish a baseline with a simple perceptual task, measured at the start and end of the session. The difference between them is your cost marker.
2. 02Work on input efficiency first. If oculomotor control isn't clean, any attentional work will run over a system already overpaying.
3. 03Introduce progressive cognitive load on already-mastered perceptual tasks: dual rules, inhibition, criterion switching.
4. 04Add controlled fatigue at the end and measure again. The goal is for the start-to-end difference to shrink over the weeks.
5. 05Transfer: reproduce the temporal structure of the real context, including its peaks and its pauses.

The role of recovery

No amount of attentional work compensates for insufficient recovery. Sleep is the highest-impact variable and also the most abused in high-demand profiles. Moderate sleep restriction degrades inhibitory control and sustained attention before almost any other function, and it does so without the person noticing: self-rated performance stays high while objective performance falls.

The structure of the day also counts. Long continuous blocks of attentional demand produce more accumulated cost than the same amount of work fragmented with real breaks. And a real break means removing the perceptual demand, not swapping one screen for another.

Closing

The second-half drop isn't a character trait or a question of wanting it enough. It's the predictable consequence of a system that has been paying a cost for every unit of information processed, and that reaches the final stretch with less margin than it needs.

Both sides of that equation can be addressed: lower the price of each operation and raise the available budget. The first route usually offers more margin and is almost never taken.

You don't lose concentration. You run out of the budget that was funding it.