Can lack of sleep make you less likely to notice your own mistakes? A new laboratory study suggests it can. Thirty healthy adults completed a demanding decision task when well rested and again after one night without sleep. After sleep deprivation, they responded more slowly, were less accurate, missed more responses and consciously detected a smaller proportion of their errors.
The useful lesson is not simply that tired people make mistakes. It is that fatigue may also weaken the internal warning system that would normally tell you to pause, check and correct one. Feeling confident is therefore not a dependable test of whether you are safe to drive, operate equipment or make an important decision after losing sleep.
Evidence checked: 26 October 2026. The research was published as an accepted manuscript in the journal SLEEP on 24 October 2026. Accepted manuscripts have passed peer review but may still change during copyediting and typesetting.
The new sleep-deprivation study at a glance
- Participants: 30 healthy adults.
- Conditions: each participant completed the task once while well rested and once after one night of total sleep deprivation.
- Task: a gamified, multi-rule Simon task designed to create measurable correct responses, errors and missed responses.
- Self-check: on every trial, participants reported their response and whether they thought that response was correct.
- Main finding: after the sleepless night, performance worsened and participants consciously detected a smaller share of their errors.
- Main limitation: this was a small laboratory experiment involving one night of complete sleep loss. It cannot tell us exactly how a particular person will perform after an ordinary short night.
What is error awareness?
Error awareness is the conscious recognition that you have just made a mistake. It matters because noticing an error can trigger a useful change in behaviour: slowing down, reviewing the last step, asking for a second opinion or correcting the problem before it grows.
Objective performance and subjective awareness are not the same thing. You can make an objectively wrong response without recognising it, or believe a correct response was wrong. The study separated these two processes by recording what happened and what each participant believed had happened after every trial.
That distinction is important outside a laboratory. A tired person may know they feel sleepy, but they may not accurately judge every lapse in attention or decision quality as it happens. Self-confidence can remain convincing even when performance has deteriorated.
What changed after one night without sleep?
The researchers found several linked changes. Responses became slower, accuracy fell, missed responses increased and the proportion of consciously detected errors decreased. The impairment also became greater as participants spent longer on the task.
The study also examined what people did immediately after a response. Both actual errors and responses believed to be errors were associated with slowing on the next trial. When rested, participants slowed more after they thought they had made an error than after an objective error alone. Sleep deprivation reduced that difference, suggesting a change in how subjective performance judgements guided subsequent behaviour.
This does not mean every tired person becomes unaware of every mistake. It means that, across this group and this task, one sleepless night reduced error awareness alongside other aspects of performance.
Why confidence is a poor fatigue check
People often manage tiredness by asking themselves whether they still feel capable. The new findings show why that question is incomplete. If sleep loss affects the process used to recognise mistakes, the person making the judgement may be working with less reliable feedback.
That matters most when an unnoticed error has consequences: driving, using machinery, preparing medication, checking measurements, handling money or making a decision that is difficult to reverse. The study did not test these activities directly, so it does not quantify risk in any one occupation. It does support the broader principle that external safeguards become more valuable when sleep has been lost.
HIGGYS already explains the wider effects of insufficient sleep in Sleep Deprivation: What Happens Without Enough Sleep. This study adds a narrower insight: performance monitoring itself may be one of the abilities affected.
Five practical ways to reduce fatigue-related errors
1. Treat lost sleep as a real constraint
Do not use motivation, experience or a burst of alertness as proof that performance is normal. If you have been awake all night or are struggling to stay alert, reduce the demands placed on you where possible.
2. Delay safety-critical tasks
Postpone driving, machinery use and difficult-to-reverse decisions when you are too tired to perform safely. The Highway Code says not to begin a journey if you are tired and to stop in a safe place if sleepiness develops.
3. Use checks that do not depend on memory
For lower-risk tasks that cannot wait, use a written checklist, slow the pace, complete one step at a time and ask a rested person to review important work. These are sensible risk controls, not a way to make severe sleep deprivation safe.
4. Protect the next sleep opportunity
Recovery depends on sleep, not simply time away from work. Give yourself an adequate sleep opportunity in a comfortable, dark and quiet environment. Read How Much Sleep Do Humans Need? for age-based guidance and the reasons individual needs vary.
5. Investigate repeated daytime sleepiness
Occasional tiredness has many ordinary causes, but persistent or unexplained fatigue can also be linked with insomnia, sleep apnoea, medicines or other health conditions. NHS guidance recommends speaking to a GP if tiredness has lasted for a few weeks, affects daily life or occurs with other symptoms.
What the study does not prove
- It does not show that one ordinary short night has the same effect as staying awake all night.
- It does not establish an exact number of errors a sleep-deprived person will miss.
- It does not test driving, furniture making, healthcare or any other real workplace activity.
- It does not show that caffeine, a mattress or any consumer product restores error awareness.
- It does not tell us how long recovery takes for every person or every type of task.
The sample was small, the setting was controlled and the paper is currently an accepted manuscript. Larger studies, different kinds of sleep restriction and real-world tasks are needed before the size and reach of the effect are clear.
Frequently asked questions
Does sleep deprivation make you unaware of every mistake?
No. Participants still detected some errors. The proportion consciously detected was lower after sleep deprivation, which describes a group-level change rather than a guarantee about any individual response.
Was this study about one short night?
No. It tested one night of total sleep deprivation. That is more severe than going to bed late and should not be treated as equivalent to every form of insufficient sleep.
Can caffeine restore normal judgement?
This study did not test caffeine. Caffeine may temporarily increase alertness, but it does not replace sleep and should not be used as proof that a severely tired person is safe to drive or perform hazardous work.
Should I drive if I feel tired but confident?
No. Confidence is not a safety measure. UK guidance says not to start a journey when tired. If you feel sleepy while driving, stop in a safe place.
Will a better mattress prevent mistakes caused by sleep loss?
No mattress can prevent the cognitive effects of staying awake. A suitable sleep surface may help reduce physical discomfort and support a comfortable sleep opportunity, but it cannot guarantee sleep or restore alertness on demand.
When should tiredness be discussed with a GP?
Seek advice if tiredness has lasted for several weeks, affects daily life or comes with symptoms such as loud snoring, gasping or choking during sleep. Do not self-diagnose the cause.
The takeaway
After one sleepless night, people in this small study did not only perform worse. They also noticed a smaller share of their mistakes. The safest response to serious fatigue is to reduce risk, use independent checks and make room for recovery sleep, rather than trusting confidence alone.
References
- Kirschner H, Tegelbeckers J, Janko D, Göde L, Ullsperger M. Sleep deprivation disrupts error awareness and subsequent behavioural regulation. SLEEP. Published online 24 October 2026. DOI: 10.1093/sleep/zsag283. Read the accepted manuscript.
- NHS. Tiredness and fatigue. Read NHS guidance.
- UK Government. The Highway Code, Rule 91. Read the driving-tiredness guidance.
This article is for general information only and is not a substitute for medical advice, diagnosis or treatment.