How Sleepy Is Your Brain Right Now?

weirdly accurate.

How Sleepy Is Your Brain Right Now?

How sleepy is my brain right now?

How sleepy your brain is right now shows in how often your attention lapses, not in how tired you feel, and the two can disagree. In Van Dongen and colleagues’ 2003 study, 48 adults spent 14 days on 4, 6 or 8 hours in bed; by the end, the 6-hour group lapsed as often as after a night without sleep, yet felt only slightly sleepy. This sleepiness test counts your lapses in about a minute and sets them beside how sleepy you say you feel.

The task is the brief psychomotor vigilance test (PVT-B), validated by Basner, Mollicone and Dinges in 2011 and used by astronauts on the International Space Station since 2009, with a sheep in place of its millisecond counter. After you rate how sleepy you feel and practise on three sheep, 12 sheep pop up behind a fence, each 1 to 4 seconds after your last tap. A reaction of 355 ms or more is a lapse; a tap with no sheep, or under 100 ms, is a false start; about 64 ms of typical browser delay is taken off every time (Pronk et al., 2020). Your alert score is the PVT-B performance score, and it and your lapses are set beside published 3-minute results for rested and sleep-deprived adults.

It is not a medical test: it cannot diagnose a sleep disorder or tell you whether you are fit to drive or work. Twelve sheep is far shorter than the original 3 minutes, so one lapse more or less moves the result a lot, and devices add delays that differ by tens of milliseconds. Read the result as a rough guide to right now.

What the test measures

One thing: how often your attention lapses right now, and whether that matches how sleepy you feel.

The task

  • Rate how sleepy you feel from 1 to 9 (our own wording, not the Karolinska Sleepiness Scale), then practise on three sheep
  • 12 sheep pop up behind a log fence, each 1–4 seconds after your last tap; tap anywhere or press a key
  • PVT-B rules (Basner, Mollicone & Dinges 2011): 355 ms or more is a lapse, a tap with no sheep or under 100 ms is a false start, 30 seconds without a tap is a lapse
  • One last question: roughly how long you slept last night

Your result

  • A playful label first, such as Well-Rested Shepherd, All-Nighter Brain, or Sleepy and Doesn’t Know It when your feeling and your taps disagree
  • Your lapses and alert score beside published results for rested adults, five nights of 4 hours in bed and 5 a.m. after a night without sleep; averages only, so no percentile
  • Your 1–9 rating against your taps, last night’s sleep against the 7 hours or more recommended for adults, every sheep charted, and one thing to change first
  • A share card with your label and alert score; a challenge link carries only your score and lapse count

Before you start

  • About a minute of sheep after a short rating and practice; free, no sign-up
  • Find a quiet minute: leaving the page breaks the timing and the sheep start over
  • Phone or computer, in a browser with 3D (WebGL) switched on; device delays differ, so small differences are noise
  • Sound is optional and never gives a sheep away; no background music
  • Your taps and your result stay on your device

Questions about sleepiness and attention lapses

Is this test free? Do I need to sign up to see my result?

Yes, it’s free, and there’s nothing to sign up for: no account, no email, no payment. Your result appears on this page the moment you finish, and you can share it or play again straight away.

How can I tell how sleepy I am right now?

Measure your attention instead of trusting the feeling. Sleep loss shows up as lapses, the odd reaction that comes very late while the rest stay normal; Basner and Dinges (2011) found lapses far more sensitive to a night without sleep than the median reaction time. And feeling misleads: in Van Dongen’s 2003 study, people on two weeks of 6-hour nights felt only slightly sleepy. The How Sleepy Is Your Brain test counts your lapses and sets them beside your own 1–9 rating.

Am I sleep deprived? Can this test tell?

It can show whether your attention right now looks rested or sleep-deprived, but one minute of sheep cannot settle it. The test sets your lapses and alert score beside published results for rested and sleep-deprived adults, and asks how long you slept. The 2015 consensus of the American Academy of Sleep Medicine and the Sleep Research Society is that adults should sleep 7 or more hours a night on a regular basis.

What is the psychomotor vigilance test (PVT)?

The psychomotor vigilance test is sleep research’s standard test of sustained attention: a millisecond counter starts at random moments and you press as fast as you can. The classic version runs 10 minutes with a 500 ms lapse line; the brief PVT-B, validated by Basner, Mollicone and Dinges in 2011, runs 3 minutes with a 355 ms line and has been used on the Space Station since 2009. This sleepiness test keeps the PVT-B’s timing and cut-offs, with a sheep for the counter.

How accurate is an online sleepiness test?

Roughly. Browsers add delay: Pronk and colleagues (2020) measured 58 to 133 ms across ten phone and laptop browsers, so about 64 ms is taken off every reaction, and the result sheet also shows your count with the fastest and slowest delays. In Grandner and colleagues’ 2018 study, a phone PVT read about 95 ms slower than the original handheld for the same 44 adults. And 12 sheep is far fewer than a 3-minute run’s roughly 65, so one lapse moves the result a lot.

How many attention lapses are normal?

About 0 to 1 in 12 sheep for a rested adult. In Basner and colleagues’ 2018 study, 45 adults in everyday life averaged 0.98 lapses on a 3-minute PVT; rested people in the 2011 sleep-lab study had about 5. Scaled to 12 sheep, that is 0 to 1, against about 2 after five nights of 4 hours in bed and about 4 at 5 a.m. after a night without sleep. The alert score compares directly: about 90% rested, 78% after the short week, 64% at 5 a.m.

Is this a diagnosis? Can it tell me if I’m safe to drive?

No. The How Sleepy Is Your Brain test is not a medical test: it cannot diagnose a sleep disorder or tell you whether you are fit to drive or work. Don’t use the result, good or bad, to decide whether to get behind the wheel; a minute of sheep cannot rule drowsiness out. If sleepiness gets in the way of your life, or you are often this sleepy despite 7 or more hours of sleep, talk to a doctor; the CDC’s About Sleep page and the American Academy of Sleep Medicine’s sleepeducation.org are reliable places to start.

Where the numbers come from

The rested and sleep-deprived values come from 3-minute PVT studies; the 2011 values are read off the paper’s graphs and rounded. Published lapse counts are scaled by 12/65, our own arithmetic: a 3-minute PVT-B holds about 65 counters. Every reaction has 63.9 ms taken off: the 67.3 ms median browser delay Pronk and colleagues measured, minus the 3.4 ms of the PVT-192 handheld used in the 2011 study. The cut-offs between labels are ours. There is no published spread of individuals, so there is no percentile, and the site does not publish its own players’ data.