Fig 1.
Schematic representation of a taxonomy for awakenings.
Fig 2.
PRISMA flow diagram summarizing the selection procedure.
Table 1.
Self-Awakening Questionnaire (English version).
The questionnaire consists of five questions aiming at probing the ability of a subject to wake up spontaneously (Question 1), and accurately (Question 4), independently from habit or circadian preference (Question 2, Question 5), or underlying conditions (e.g., stress, anxiety; Question 3).
Table 2.
Results of the literature review.
“Experiment type”: location of the experiment and type of objective sleep validation (PSG = polysomnography, EEG = electroencephalography; EOG = electrooculography; Act = Actigraphy); in case of multiple studies within a paper, S1 indicates the first and S2 the second study. “Sleep type”: nocturnal or diurnal sleep. “Nr. Participants”: total experimental sample size. “Age (SD)”: age range or average for the whole participant group and corresponding standard deviations (SD) when available. “Successful criterion”: criterion used to define a successful self-awakener, usually a time window around the expected awakening time (absolute value in minutes). “Nr. SA”: number of self-awakeners explicitly reported in the study or whether the study investigated successful self-awakening events. “% SA/total”: percentage of self-awakeners on the study sample size either reported in the manuscript or calculated based on the available data. “SA age (SD)”: age of self-awakeners and its standard deviation. Additional notes, symbols, and abbreviations: *15 participants were recruited but only 12 underwent EEG. ** depending on the questionnaire question and concerning the ability to wake-up with or without an alarm; *** five participants follow within the second criterion and are considered “moderately successful”; § = studies designed to select only self-awakeners; # = 9 self-awakeners were identified but data of one were lost, leaving 8 participants; ## = PSG failed for one participant, leaving 8 participants (6 F; mean age = 21.8 ±.6 years).
Fig 3.
Differences between Self-Awakeners (n = 9) and non-Self-Awakeners (n = 144) by test scores.
The difference between groups was non-significant for all measures. For all boxplots, each box contains the interquartile range (i.e., the range containing 50% of all observations) and the median value (middle line), while the whiskers represent values extending outside 50% of the observations. Abbreviations: ISI = Insomnia Severity Index; MEQ = Morningness-Eveningness Questionnaire; PSQI = Pittsburgh Sleep Quality Index; PSWQ = Penn State Worry Questionnaire STAI = State-Trait Anxiety Inventory; BDI = Beck Depression Inventory RRS = Ruminative Response Scale; PSAS = Pre-Sleep Arousal Scale; CES = Center for Epidemiologic Studies Depression Scale (see S1 File for details).
Fig 4.
Distribution of the SAQ scores depending on the respondent’s circadian preference group.
Each boxplot contains the interquartile range (i.e., the range containing 50% of all observations) and the median value (middle line), while the whiskers represent values extending outside 50% of the observations.
Fig 5.
Proposed schematic model of the cognitive operations potentially involved in self-awakening.