Sleep Chart
Introduction
Sleep is vital for learning. To sleep well and to learn well, you need to understand your own circadian rhythm. Timeline in SuperMemo was designed to assist you in that task. It can help you optimize the timing of sleep as well as the timing of your learning. You can inspect the timeline of learning generated automatically, and log your sleep data manually. Collecting your sleep data can be useful in understanding the link between sleep and learning.
At minimum skill level, you can use Timeline for basic visual inspection of your favorite learning and sleep hours. However, more advanced functions such as optimizing the time for learning or the time for sleep require advanced analysis and understanding of circadian rhythms. Currently, the toolset for analysing the impact of sleep on learning is very limited. However, if you start logging your sleep data today, you will be able to use future, more advanced versions of SuperMemo to study and understand your sleep and learning.
Repetitions timeline
The timeline of repetitions is collected automatically and is separate for each collection. Each time your make repetitions, the learning block is added to the timeline.
Sleep timeline
The timeline of sleep must be logged manually and is common to all collections. To log a block of sleep, click the beginning of the block (sleep start) and then click the end of the block (sleep end). You can also start from clicking the end of sleep first. Sleep blocks above 22 hours are disallowed. Sleep blocks cannot overlap with repetitions timeline (you cannot learn with SuperMemo and be asleep at the same time). If you have already collected your sleep data in SleepChart, you can import this data with File : Import SleepChart file. If you import files from SleepChart, you can test for sleep and learning overlaps with Edit : Test for block overlaps. You can mark blocks of forcefully delayed sleep, as well as mark blocks cut short with an alarm clock or other factors. Please note that you can get best analytical results if you do not artificially regulate sleep (e.g. with an alarm clock, sleeping pills, etc.). Applied models will not fully account for artificial intervention. Last but not least, natural sleep is what you should aim for in learning as well as for the sake of maximum health and well-being. Natural free-running sleep will maximize your fun in life!
Timeline graphs
Currently you can use 5 analytical graphs in Timeline. This set is likely to grow in future releases of SuperMemo as more gets to be known about information that can be extracted from correlations found in sleep&learning data. If you deem the presented analytical power as insufficient today, it should not stop you from collecting sleep data. Start today! Every data point can contribute to valuable conclusions in the future.
Timeline
Timeline displays repetitions blocks of the current collection (in red) and sleep blocks (in blue). Dates and total repetition time are displayed on the right. Sleep blocks can be consolidated with Consolidate button on the toolbar. For example, if you woke up for 5-10 min. in the night, consolidation will make SuperMemo treat the entire night block as a single entity (short awakenings are a frequent occurrence, even if we are not aware of them, and have little impact on learning). Sleep optimization data can be displayed in this graph. Most importantly, two independent models are used to predict middle-of-the-night points as well as the expected optimum retirement and awakening times. Those approximations may be helpful in optimizing sleep in people who work shifts or sleep in irregular hours for various reasons. For example, after a week of irregular sleep, it may be difficult to determine the optimum retirement hour that is likely to produce best quality sleep. Going to sleep too early might result in premature awakening (which may often ruin the night sleep entirely). Going to sleep too late may result in short night sleep, sleep deprivation, and reduced alertness on the following day. Predicting optimum sleep time on the basis of sleep history is inexact science, and two models used may produce different outcomes. Important! Your natural instinct should always take precedence over mathematical models. Moreover, best results in sleep optimization are accomplished in free-running sleep. If you use an alarm clock, or force yourself awake through the night, or take sleeping pills, the models may not adequately account for the chaotic change that is occurring in your sleep control systems.
It is impossible to provide a sure&simple way of interpreting the following graphs. Only rough guidelines are provided. For more detailed interpretation, send your data to sleep2009(AT)supermemo(DOT)com. Your data will be used to improve future analytics. If possible, you will also receive personal help in interpreting your results.
Circadian
Circadian graph plots your favorite sleep times as counted from natural awakening (blue homeostatic line), as well as the resulting average sleep length produced by various retirement hours (red circadian line). If you are trying to determine your optimum sleep time, see for peaks in the blue homeostatic line and choose near points that produce sufficiently long sleep (high reach of the red curve). In nappers, the blue line should also point to the maximum mid-day alertness dip. However, in this case, short naps may actually be a sign of well-timed naps (if not taken too early in reference to the blue homeostatic line).
Phase shift
Phase shift graph is helpful in people practising free-running sleep who suffer from a degree of phase-shift (ASPS or DSPS). In free-running sleep, this graph will display the degree of phase-shift as well as its dependence on the time of the day.
Alertness
In a healthy individual who is not sleep deprived and who sleeps in the correct phase, the best learning results are obtained early in the morning and after a siesta. You can see how fast your alertness (and grades) drop during the day by inspecting the Alertness graph. In this graph, you can see the time that has passed since the last sleep block, and how grades change in waking phase. The minimum length of sleep blocks that are considered is determined by Min. sleep block (h) box (0.2 hours, or 12 min. is the default minimum sleep block taken into consideration).
If you have already collected your sleep data with SleepChart, you can see your wake-grade correlation with SuperMemo 2008. However, only repetitions executed with SuperMemo 2006 (or later) will count (earlier SuperMemos did not store precise time of repetitions in repetition history).
Distribution
This graph tells you how long your usual sleep blocks are. For example, is it true that your sleep blocks form a multiple of 90 min. (or some similar ultradian cycle)?
SuperMemo: Distribution graph makes it possible for you to tell how long your usual sleep blocks are
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Two-component sleep model
SuperMemo uses a two-component sleep model inspired by the publications of Alexander A. Borbély and Peter Achermann. Unlike other models, SuperMemo uses your sleep data to predict the homeostatic and circadian status of your alertness. This may be helpful in choosing the optimum time for learning on a given day (given a particular history of sleep). This can also help you plan your sleep many hours in advance if your sleep pattern is highly irregular. The model does not predicate on the timing and duration of REM and NREM sleep episodes.
Important! This is the first release of the presented model to a wider public and should only be used for educational purposes as well as an inspiration in planning your sleep and learning. There are individual genetic differences that affect the length of the circadian cycle, steepness of the homeostatic decline in alertness, sleep length preference, sleep architecture, etc. This model is limited in accounting for these variables. If you are sleepy against the simulations based on the model, you can probably trust your own instincts better. If you feel alert against the simulations based on the model, you can certainly get down to learning and ignore predictions of the model. Moreover, sleep patterns are a good measure of your sleep control systems only if they are not artificially disturbed (e.g. by forcefully delaying sleep, using alarm clock, using sleeping pills, etc.). In other words, the presented model may fail to map your circadian rhythms correctly, if you are not free running your sleep. You can mark blocks as artificially shortened or delayed (Forced awakening and Delayed retirement on the context menu available with a right-click). However, marked blocks will have a limited effect as there is no way of knowing the degree of the cut into the sleeping patterns, and, consequently, knowing the resulting perturbation in the control system produced by artificially modified sleep.
To see the predictions of the model for any given day, make sure you have your sleep data filled out for recent days, and shift-click the day in question.
To see a more accurate reflection of the homeostatic decline in alertness during wakefulness, see the Alertness tab.