#Note/Permanent #CognitiveScience #Productivity #Health/Sleep ## Summary This note examines how subjective alertness and cognitive performance fluctuate throughout the day and in response to sleep patterns. Key observations include: 1. **Peak Alertness and Cognitive Performance Post-Wake**: Subjective alertness and cognitive performance typically peak a few hours after waking up and then gradually decline as the day progresses, reaching their lowest before sleep. 2. **Late Nights and Decreased Alertness**: Staying up late can lead to lower levels of alertness and increased error-proneness. 3. **Sleep Deprivation Lowers the Peak**: If one does not sleep, subjective alertness and cognitive performance will partially rebound during the next day's awake time but will not reach the usual peak levels. 4. **Adjusting to New Sleep Schedules**: For individuals who must shift their sleeping schedules, such as adjusting to jet lag or day/night working shifts, subjective alertness remains high in the first half of the day. However, it drops more rapidly and sooner, leading to quicker fatigue compared to maintaining a stable sleeping schedule. ## Usual Sleep/Wake Schedule vs. Staying Up Late This study identifies three phases correlating with alertness and cognitive performance throughout the day and during periods of extended wakefulness ![[Sleep and performance.png]] ### Phase 1 - First 16 hours after waking up Independent of an individual's [chronotype](https://en.wikipedia.org/wiki/Chronotype) (morningness or eveningness), daily activities typically occur in the first 16 hours post-waking. During this period, both subjective alertness and cognitive performance peak within the first few hours, then gradually decline with slight fluctuations. ### Phase 2 - The last 8 hours after waking up Normally, after 16 hours of wakefulness, people sleep for about 8 hours to complete a circadian cycle. However, if one stays awake beyond this, alertness and cognitive performance can drop drastically, often leading to slower reaction times and increased errors. ### Phase 3 - First 16 hours after sleep deprivation When individuals are kept awake for 24 hours, the subsequent day shows a temporary improvement in alertness and performance compared to the end of the wakeful period, but these levels are still significantly lower than after a normal night's sleep. ## Shift Work and Jet Lag The study also simulated the effects of shift work or jet lag on subjective alertness and cognitive performance, noting the drastic changes compared to regular sleep patterns. ![[desync sleep performance.png]] ### Phase 1 - First 7-8 hours after waking up Individuals adjusting to a new sleep schedule typically experience stable or increasing subjective alertness and cognitive performance in the first 7-8 hours after waking. ### Phase 2 - The following 7-8 hours After the initial stable period, there is a marked decrease in both alertness and cognitive performance, often dipping below baseline levels. ### Reference - [Circadian and sleep/wake dependent aspects of subjective alertness and cognitive performance](https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2869.1992.tb00021.x)