What this tool actually measures
The Sleep-Cognition Optimizer measures your current behavioral sleep patterns — what your sleep is actually doing right now, not what your body would prefer if life imposed no schedule. That biological/trait preference is measured separately by the companion Chronotype Test.
From your observed sleep timing on workdays vs. free days, the Optimizer computes three behavioral metrics: your behavioral chronotype (using the MSFsc methodology, Roenneberg 2003), your social jetlag (the weekday-vs-free-day midsleep gap), and a regularity estimate, the tool's own score from 0 to 100 for how steady your sleep looks across the week. It borrows its idea from the Sleep Regularity Index of Phillips et al. (2017) but is not that index.
When the Chronotype Test has also been taken in the same browser, the Optimizer computes the biology-behavior gap: the difference between the chronotype score your Chronotype Test answers give (trait) and the score your sleep times here give (state). It shows how far your current sleep times sit from the times your Chronotype Test answers describe; it compares two of this site's scores and is not a clinical measure.
The tool then sets out a personalized schedule built from your must-wake time and the time you take to fall asleep, and five levers (caffeine cutoff, exercise timing, wind-down, cognitive task scheduling and sleep timing consistency) in the order your goal sets.
Why the tool looks at behavior, not only chronotype
Whether you are a morning or evening type is only part of the picture. The Optimizer also estimates two things your answers can show: how far your workday sleep sits from your free-day sleep, and how regular your sleep timing is.
Social jetlag: The construct was introduced by Wittmann et al. (2006). The Arab et al. 2024 meta-analysis (n = 231,648 across 43 studies) found social jetlag linked with slightly higher BMI, body fat and waist circumference (for BMI, r = 0.12), a link its authors say needs further work to show cause.
Sleep regularity: The Sleep Regularity Index of Phillips et al. (2017) measures how often a person is asleep or awake at the same clock times 24 hours apart, from night-by-night sleep records; in their study of college students, less regular sleep went with later sleep timing and lower grades. Four typical times cannot give that index, so the Optimizer gives its own regularity estimate instead: it starts at 100 and takes off up to 40 points for social jetlag, up to 20 for the difference between your workday and free-day night lengths and up to 12 for night waking. It has no target and cannot be compared with the published index's values.
This is why the Optimizer puts these behavioral figures first rather than treating chronotype as the headline: your sleep times are something you can change, and the figures show where they stand now.
How your personalized schedule is generated
The recommended schedule starts from your hard constraint, your must-wake time (Q10), and the time you take to fall asleep (Q6). The sleep window follows the same rule for everyone; your chronotype score moves only the estimated cognitive peak, and your answers about caffeine, exercise and your demand window are scored against the schedule.
Sleep window: 7.5 hours of sleep, a planning default inside the 7 to 9 hours commonly advised for adults (Hirshkowitz et al. 2015), is subtracted from your must-wake time to give the time you fall asleep; lights-out is that time less how long you take to fall asleep, counted once.
Cognitive peak window: An estimate shifted by your chronotype score: a two-hour window that starts three hours after your must-wake time for a score of 50, earlier for a more morning score and later for a more evening one. The 2025 systematic review of synchrony effects (Chauhan et al., Chronobiology International, 65 studies) found the synchrony effect in approximately 45% of younger-adult studies and 83% of older-adult studies — real but modest. We do not oversell this.
The five levers, each scored from 0 to 100:
- Caffeine cutoff: 7 hours before you fall asleep on your target night. In Drake et al. (2013), caffeine taken even 6 hours before bed reduced sleep. Only a last drink after the cutoff loses points.
- Exercise timing: finished 3 hours before you fall asleep. Stutz et al. (2019) found evening exercise did not disrupt sleep overall, though vigorous exercise ending within an hour of bedtime could; the 3 hours is the tool's margin. Only exercise after that time loses points.
- Wind-down: the hour before lights-out; its score comes from how long you take to fall asleep (Q6).
- Cognitive task scheduling: your demand window (Q11) against the estimated peak, 25 points for each window between them. Analytical work suits the peak; creative work may benefit from off-peak times (weakened inhibitory control can aid insight).
- Sleep timing consistency: scored by the regularity estimate; the aim is free nights within 45 minutes of workday nights.
Your goal (Q12) decides which lever comes first: sleep regularity, a smaller biology-behavior gap and less social jetlag put sleep timing consistency first, peak cognitive performance puts cognitive task scheduling first, and better mood and energy puts first whichever lever scores lowest.
The biology-behavior gap (when both tools are taken)
The biology-behavior gap is the absolute difference between your trait chronotype (from the Chronotype Test) and your behavioral chronotype (derived from your observed sleep timing here), both on the same 0 to 100 scale.
The four labels are this tool's own conventions, not clinical thresholds:
- Well-Aligned (gap < 10): your sleep times sit close to the times your Chronotype Test answers describe.
- Mild Misalignment (10–19): they sit a little away from them.
- Moderate Misalignment (20–34): they sit well away from them.
- Severe Misalignment (35+): they sit far from them.
If you have not taken the Chronotype Test, the Optimizer still produces a full schedule and the five levers — but cannot compute the gap.
How to use your result
The recommended schedule is a starting point, not a prescription. Sleep adapts gradually, so move it in small steps.
First: if your lights-out now is later than the target, move it earlier in 15-minute steps, holding each step for a few nights, and keep free nights close to workday nights.
Then: hold the target night once you reach it, and note how long you take to fall asleep and how alert you feel in the morning.
After about four weeks: take the Optimizer again with your new times and compare your social jetlag and regularity estimate with today's.
If the recommended schedule conflicts with your life circumstances — for example, a Strongly Evening chronotype and an unmovable 6 AM work start — the other levers (caffeine timing, exercise and wind-down) still apply. If falling asleep takes 45 minutes or more, or you often struggle to fall back asleep, talk to a doctor before moving your bedtime earlier: an earlier lights-out can mean more time lying awake.
Frequently asked questions
How does the personalized bedtime routine builder work?
Answer 12 questions about your current sleep timing, wake-time constraints, chronotype, caffeine and exercise timing, and cognitive demands. The tool uses those inputs to build a personalized bedtime, wake time, wind-down start, caffeine cutoff, exercise window, and cognitive task schedule. It is an educational planning tool, not a medical diagnosis or treatment plan.
What does the LBL Sleep-Cognition Optimizer do?
The Optimizer asks 12 questions about your actual current sleep timing, sleep quality, and lifestyle context. It then computes your behavioral chronotype (derived from your observed midsleep on free days), your social jetlag (the weekday-vs-free-day gap), its own regularity estimate, and—if you've taken the Chronotype Test—your biology-behavior gap. It then sets out a personalized schedule with lights-out, wake time, an estimated cognitive peak window, and five levers in the order your goal sets.
How is this different from the Chronotype Test?
The Chronotype Test measures your biological/trait chronotype — what your body would prefer if life imposed no schedule. The Optimizer measures your behavioral chronotype — what your sleep actually looks like right now. The gap between them shows how far your current sleep times sit from the times your Chronotype Test answers describe. Taking the Chronotype Test first lets the Optimizer show that gap.
What is the biology-behavior gap?
If you've taken both the Chronotype Test and the Optimizer in the same browser, the Optimizer computes the absolute difference between your biological chronotype (from the Chronotype Test) and your behavioral chronotype (derived from your observed sleep timing). The tool labels a gap of 10+ points mild misalignment, 20+ moderate and 35+ severe; the labels are its own conventions, not a clinical measure.
What is social jetlag?
Social jetlag is the difference between your midsleep time on workdays vs. free days. If you sleep 11 PM–6:30 AM on workdays (midsleep 2:45 AM) but 1 AM–9 AM on free days (midsleep 5:00 AM), your social jetlag is 2 hours and 15 minutes. The construct was introduced by Wittmann et al. 2006; studies link larger social jetlag with modestly higher body weight (Arab et al. 2024), a link not yet shown to be a cause.
What is the regularity estimate?
The Sleep Regularity Index (SRI) of Phillips et al. (2017) measures how often a person is asleep or awake at the same clock times 24 hours apart, from night-by-night sleep records. Four typical times cannot give that index, so this Optimizer gives its own regularity estimate from 0 to 100: it starts at 100 and takes off up to 40 points for social jetlag, up to 20 for the difference between your workday and free-day night lengths and up to 12 for night waking. It has no target and cannot be compared with the published index's values.
Why does this tool ask about caffeine and exercise?
Caffeine late in the day can cut sleep: in Drake et al. (2013), even a dose taken 6 hours before bed reduced it. The Optimizer sets your caffeine cutoff 7 hours before the time you fall asleep on your target night, and your exercise cutoff 3 hours before it, a wider margin than the hour of vigorous exercise Stutz et al. (2019) found could disrupt sleep. Only a last drink or a workout after its cutoff loses points; an earlier one scores in full.
Do I need to take the Chronotype Test first?
Not required. Without a Chronotype Test result in this browser, the Optimizer still computes your behavioral chronotype, social jetlag, regularity estimate and a personalized schedule; it just cannot compute the biology-behavior gap. Question 1 asks for your closest chronotype match either way, and your result shows it beside the chronotype your sleep times give.
What if my schedule varies a lot?
Use your typical pattern. If you genuinely have no consistent timing (e.g., rotating shift work), the Optimizer's recommendations will be limited — sleep optimization for irregular shifts requires specialized clinical guidance. For most people with typical workday/free-day patterns, answer based on your modal behavior, not your outliers.
Why is the recommended schedule sometimes different from a "normal" sleep schedule?
Because it starts from your own must-wake time and the time you take to fall asleep, not from one clock time for everyone: 7.5 hours of sleep before your must-wake time, with lights-out earlier by how long you take to fall asleep. Your chronotype moves the estimated cognitive peak, not the bedtime, and your caffeine, exercise and demand-window answers are scored against that night.
What about light exposure recommendations?
Light timing is the strongest zeitgeber and a powerful intervention lever. However, light timing recommendations require careful individual specification—lux levels, timing windows, blue-light wavelengths—and a self-report tool cannot capture the inputs needed to prescribe well. We acknowledge light's importance without making specific recommendations in v1. Future versions may add this with wearable integration.
How long does this take?
Most users complete the 12 items in 3–4 minutes. The behavioral sleep timing items (Q2–Q5) take the longest because they require recalling your typical times.
Is my data saved?
Scoring for this page runs in your browser. The Save to my browser button keeps your results only in this browser's own storage, and they are not sent to LifeByLogic. If you choose to save your result to a free LifeGraph+ account, your chronotype, your regularity estimate, your social jetlag, your weekly sleep duration and your four alignment scores are kept there with the date. If you buy The Bedtime Bridge, your 12 answers, and your Chronotype Test score when you have one, go to checkout so your report can be written. We use Google Analytics 4 for aggregate page-level usage, never with your answers or results. You can also download your result as a JSON file for personal record-keeping.
How to cite this tool
LifeByLogic. (2026). Sleep-Cognition Optimizer (Version 1.0) [Interactive web tool]. https://lifebylogic.com/brain-lab/sleep-cognition-optimizer/
References
- Arab A, Karimi E, Garaulet M, Scheer FAJL. Social jetlag and obesity: A systematic review and meta-analysis. Obesity Reviews. 2024;25(3):e13664.
- Chauhan S, Vanova M, Tailor U, et al. Chronotype and synchrony effects in human cognitive performance: A systematic review. Chronobiology International. 2025;42(4):463-499.
- Drake C, Roehrs T, Shambroom J, Roth T. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine. 2013;9(11):1195-1200.
- Hirshkowitz M, Whiton K, Albert SM, et al. National Sleep Foundation's sleep time duration recommendations: methodology and results summary. Sleep Health. 2015;1(1):40-43.
- Jones SE, Lane JM, Wood AR, et al. Genome-wide association analyses of chronotype in 697,828 individuals provides insights into circadian rhythms. Nature Communications. 2019;10(1):343.
- Kantermann T, Sung H, Burgess HJ. Comparing the Morningness-Eveningness Questionnaire and Munich ChronoType Questionnaire to the Dim Light Melatonin Onset. Journal of Biological Rhythms. 2015;30(5):449-453.
- Lunsford-Avery JR, et al. Validation of the Sleep Regularity Index in older adults and associations with cardiometabolic risk. Scientific Reports. 2018;8:14158.
- Phillips AJK, Clerx WM, O'Brien CS, et al. Irregular sleep/wake patterns are associated with poorer academic performance and delayed circadian and sleep/wake timing. Scientific Reports. 2017;7:3216.
- Roenneberg T, Wirz-Justice A, Merrow M. Life between clocks: Daily temporal patterns of human chronotypes. Journal of Biological Rhythms. 2003;18(1):80-90. [MSFsc methodology — cited as open scientific method; MCTQ instrument not administered]
- Roenneberg T, Allebrandt KV, Merrow M, Vetter C. Social jetlag and obesity. Current Biology. 2012;22(10):939-943.
- Stutz J, Eiholzer R, Spengler CM. Effects of evening exercise on sleep in healthy participants: A systematic review and meta-analysis. Sports Medicine. 2019;49(2):269-287.
- Wittmann M, Dinich J, Merrow M, Roenneberg T. Social jetlag: Misalignment of biological and social time. Chronobiology International. 2006;23(1-2):497-509.