Polymorphisms in genes of circadian system family seem to be of most importance for understanding of mechanisms underlying self-assessed individual variation in morning–evening preference. A review of earlier reported positive findings indicated that, at least, four polymorphisms in period circadian clock 3 (PER3) showed significant association with, at least, one of sub-constructs of a morningness–eveningness scale. However, similar to other candidate gene studies, these studies suffer from increased likelihood of false positive findings. We tried to replicate some of the most recently published positive results on associations of sub-traits of morningness–eveningness with two PER3 non-synonymous single nucleotide polymorphisms. DNA from buccal swabs was collected from healthy residents of three Russian cities, Moscow (N = 149) and Novosibirsk and Stavropol (N = 248). The tested hypotheses were formulated in accord with the earlier reported positive findings: the rare alleles might be linked to a higher score on (i) morning earliness–lateness scale (rs2640909, Moscow data-set) and (ii) both morning and evening earliness–lateness scales (rs228729, Novosibirsk and Stavropol datasets). The results provided support for the former hypothesis. These and earlier reported results highlighted several critical issues that remained to be addressed in future independent replications of positive findings on potential genetic markers for morning and evening earliness–lateness.

Sub-constructs of morning–evening preference might be differentially related to polymorphisms in circadian clock genes. We previously reported significant association between a single nucleotide polymorphism in PER3 (rs2640909) and Morning but not Evening Lateness scale of the Sleep–Wake Pattern Assessment Questionnaire. To further explore such a scale-specific relationship, seven single nucleotide polymorphisms in five circadian clock genes were studied using exploratory and confirmatory samples (in total, n = 698). The association of rs2640909 with Morning Lateness scale was not replicated in the confirmatory sample but remained significant in the merged sample. Moreover, we found and confirmed an association of this scale with rs1159814 in RORα. The results provided further evidence for differential relationship of polymorphisms in circadian clock genes with morning and evening components of morning–evening preference. We also suggested possibility to take into account the pattern of geographic variation in allele frequency for prioritization of circadian clock polymorphisms in candidate gene studies.

Under national “lockdown,” the habitual late risers need not wake up early, and, similarly to the early risers, they don’t lose much sleep on weekdays. We tested whether, despite a decrease in weekday sleep loss, the difference between distinct chronotypes in health and sleep problems persisted during “lockdown.” Two online surveys were conducted from 10th to 20th of May, 2020 and 2021, one of them after 6 non-working weeks and another after 14 working weeks (during and after “lockdown,” respectively). Participants were students of the same grade at the same university department (572 and 773, respectively). The self-assessments included the Single-Item Chronotyping (SIC) designed for self-choosing chronotype among several their short descriptions and several questions about general health, mood state, outdoors and physical activity, and sleep concerns. The results suggested that the responses to each of the questions were not randomly distributed over 6 distinct chronotypes. Such a nonrandomness was identified within each of three pairs of these chronotypes, evening vs. morning types (with a rising throughout the day vs. a falling level of alertness, respectively), afternoon vs. napping types (with a peak vs. a dip of alertness in the afternoon, respectively), and vigilant vs. lethargic types (with the levels of alertness being permanently high vs. low, respectively). Morning, afternoon, and vigilant types reported healthier sleep/mood/behavior/habits than three other types. The most and the least healthy sleep/mood/behavior/habits were reported by morning and evening types, respectively. These relationships with health and sleep problems and the frequencies of 6 chronotypes remained unchanged after “lockdown.” Such results, in particular, suggested that the association of evening types with poorer health and sleep might not be attributed to a big amount of weekday sleep loss. The accounting for this association might help in designing interventions purposed on reduction of sleep and health problems.

The circadian phase difference between morning and evening types is a fundamental aspect of chronotype. However, results of categorizations into chronotypes based on reported sleep times show low concordance with those based on measurements of the hormonal or physiological or molecular rhythm–markers of the circadian phase. This might be partially explained by the profound individual differences in the phase angle between the sleep–wake cycle and these rhythms that depends on chronotype, age, sex, and other factors. Here, we examined the possibility of using self-reported sleep times in the condition of 5-days-on/2-days-off school/work schedule to estimate circadian phase differences between various chronotypes. In an in silico study, we determined that, for such an estimation, similarities of the compared chronotypes in weekend sleep duration and weekend–weekday gap and in risetime are required. In the following empirical and simulation studies of sleep times reported by 4940 survey participants, we provided examples of the estimation of circadian differences between chronotypes, and the model-based simulations of sleep times in morning and evening types exemplified a way to confirm such estimations. The results of in silico, empirical, and simulation studies underscore the possibility of using bedtimes and risetimes for direct estimation of the circadian phase differences between individuals in real-life situations, such as a 5-days-on/2-days-off school/work schedule. Additionally, the results of these studies on different chronotypes provided further mathematical modeling and empirical evidence for our failure to sleep more on weekends to recover/compensate/pay back/ catch up on lost sleep.

Background: Our work/study culture is biased towards the circadian clocks of “morning types”, whereas “evening types” are forced to advance their weekday waking times relative to weekend waking times. Since the experimental research consistently reveals a >2 h difference between these two chronotypes in the positions of their endogenous circadian phases, we hypothesized the necessity to permit a >2 h difference between them in weekday waking times to equalize their irrecoverable loss in sleep on weekdays. Methods: A total of 659 and 1106 participants of online surveys identified themselves as morning and evening types, respectively. The hypothesis was tested by applying a model of sleep–wake regulation for simulating sleep times reported by 245 lecturers of these two types, and by comparison of sleep times of these types among these lecturers and 1520 students. Results: The hypothesis was supported by results showing that, if, on weekdays, an “average” morning type wakes at 6 a.m., the equalization of the weekday sleep loss of the two chronotypes would require the waking time of an “average” evening type to be no earlier than 8 a.m. Conclusions: These results may be implemented in a model-based methodology for the correction of weekday waking times to equalize weekday sleep loss.

The article presents the results of a pilot study of the perception of the demotivator and meme genres. It was a part of an experimental study of psychophysiological and psycholinguistic features of perception and understanding of multimodal extremist texts. The aim of the study is to develop and test the hypothesis about the influence of genre on perception of multimodal texts. To test the hypothesis, we analyze the respondents' eye movement data from the main experimental study (n = 60; 31 forensic linguists with anti-extremism practice, 29 non-experts). Research methods were eye-tracking and quantitative data processing. The following statistically reliable data were obtained: compared to memes, respondents looked at demotivators (1) for a longer time, made (2) shorter fixations, (3) with more of them, and also made (4) faster and (5) shorter saccades. These parameters may indicate a denser scanning pattern of viewing demotivators compared to memes and greater cognitive expenditure in assessing the semantic content of demotivator texts. The results of the study suggest a connection between genre and the degree of multimodal texts perception complexity. This provides an opportunity for further research in this direction and, in the future, will enable the development of norms of cognitive load of judicial linguists who analyse multimodal extremist texts.