Arash Rahafar

Morningness–eveningness and amplitude – development and validation of an improved composite scale to measure circadian preference and stability (MESSi)

ABSTRACT Measuring morningness–eveningness is an important aspect of individual differences because it is associated with many aspects of personality and health. The present study outlines recent advancements in the field of measurement and proposes an improved assessment of morningness–eveningness, such as the measurement of circadian amplitude, updating and reflecting new item developments, addressing the clock time based measures, the morning-biased items and the aspect of uni versus multidimensionality. Four studies have been carried out in Germany to present a novel development (with a total sample of N = 1181). In study I, the exploratory factor analysis (EFA) revealed three dimensions, one of morningness, one of eveningness and one of amplitude/stability. Then, items were reduced to present a clearer factor structure by removing ambiguous items. In the second study, a shortened questionnaire was applied, with 15 items (5 per construct), but Confirmatory Factor Analysis (CFA) did not provide acceptable fit indices. Refining items were made in study III, which again showed a clearer factor structure in EFA, and subsequently, in study IV, the refined set of 15 items provided a good fit of a CFA. The final questionnaire was tested for validity by applying clock times, personality questions and alertness ratings. Thus, this newly developed questionnaire contains three distinct dimensions. To reflect the new content, the scale is labelled morningness–eveningness-stability-scale improved (MESSi).

Latitude affects Morningness-Eveningness: evidence for the environment hypothesis based on a systematic review

Morningness-eveningness (M/E) is an individual trait related to a person’s sleep-wake cycle and preference for morning or evening hours. The “environment hypothesis” suggests that M/E is dependent on environmental factors, such as latitude, mean average temperature and photoperiod. We here analyzed a large number of datasets to assess this effect based on a systematic review. Data were from a total of 87 datasets and 35,589 individuals based on 28 countries. Partial correlations correcting for age revealed significant relationships between M/E and latitude, mean yearly temperature, photoperiod and sunset. Evening orientation was related to higher latitude, longer days and later sunset. Morning orientation was related to higher average temperatures. Percentage of females and sunrise time had no significant influence. These variables (sunset, temperature, photoperiod) were then input in a general linear model. The full model showed an influence of age and of sunset on CSM scores, but not of photoperiod and average temperature. Sunset, therefore, seems to be the most important statistical predictor for the observed latitudinal gradient.

Morningness-eveningness in a large sample of German adolescents and adults

People differ in their sleep-wake behavior. This individual difference is conceptualized in different aspects, such as wake up times, bed times, times of peak performance, as well as in morning affect. A total of 14,987 visitors of an exhibition in the LWL State Museum of Natural History, Münster (Germany), did the survey on chronotype and gave their consent that these data can be used for a scientific study. Age groups were coded into 5-year bins. Mean age (mean ± SD) was 28.2 ± 17.5 years. There were 8075 females (54%) and 6912 males in the sample. The German version of the rMEQ (reduced Morningness-Eveningness-Questionnaire) was used for data collection. The data showed clear age effects. Younger children are more morning oriented and become rapidly evening oriented during puberty, while the more attenuated turn towards morningness occurs from the age of 20 years. Then between the ages 25 to 30 morningness-eveningness remained rather stable. Significant gender differences existed in the reproductive age, i.e., the age groups 20 to 50 (corresponding to the age 16–50 years). In other age groups, no gender differences could be detected. Seasonal effects were also found. Chronotype score was lowest during the summer months (and more evening oriented). Based on the single item analysis of the five questions of the rMEQ, we found age group differences in all items. Gender differences occurred in all items except item 1, which deals with the preferred wake-up time. Men always scored significantly lower (i.e. more evening oriented) than women except in item 2 (tiredness after awakening). Seasonal effects were only significant in item 3, which is related to preferred bed times. People showed a later bed time preference during summer. The classification of chronotypes according to the cut-off scores provided by Adan and Almirall (1991) and by using the 20/80 percentile provided identical cut-off scores (values of 11 and below for evening types and 18 and above for morning types).

The role of chronotype, gender, test anxiety, and conscientiousness in academic achievement of high school students.

ABSTRACT Previous findings have demonstrated that chronotype (morningness/intermediate/eveningness) is correlated with cognitive functions, that is, people show higher mental performance when they do a test at their preferred time of day. Empirical studies found a relationship between morningness and higher learning achievement at school and university. However, only a few of them controlled for other moderating and mediating variables. In this study, we included chronotype, gender, conscientiousness and test anxiety in a structural equation model (SEM) with grade point average (GPA) as academic achievement outcome. Participants were 158 high school students and results revealed that boys and girls differed in GPA and test anxiety significantly, with girls reporting better grades and higher test anxiety. Moreover, there was a positive correlation between conscientiousness and GPA (r = 0.17) and morningness (r = 0.29), respectively, and a negative correlation between conscientiousness and test anxiety (r = –0.22). The SEM demonstrated that gender was the strongest predictor of academic achievement. Lower test anxiety predicted higher GPA in girls but not in boys. Additionally, chronotype as moderator revealed a significant association between gender and GPA for evening types and intermediate types, while intermediate types showed a significant relationship between test anxiety and GPA. Our results suggest that gender is an essential predictor of academic achievement even stronger than low or absent test anxiety. Future studies are needed to explore how gender and chronotype act together in a longitudinal panel design and how chronotype is mediated by conscientiousness in the prediction of academic achievement.

Cross-cultural validity of Morningness-Eveningness Stability Scale improved (MESSi) in Iran, Spain and Germany

ABSTRACT Morningness-Eveningness Stability Scale improved (MESSi) is a newly constructed measure to assess circadian types and amplitude. In this study, we applied this measure to participants from three different countries: Germany, Spain and Iran. Confirmatory factorial analysis (CFA) of MESSi displayed mediocre fit in the three countries. Comparing increasingly stringent models using multigroup confirmatory factor analyses indicated at least partial measurement invariance (metric invariance) by country for Morning Affect and Distinctness subscales. Age was positively related to Morning Affect (MA), and negatively related to Eveningness (EV) and Distinctness (DI). Men reported higher MA than women, whereas women reported higher DI than men. Regarding country effect, Iranian participants reported highest MA compared to Spaniards and Germans, whereas Germans reported higher DI compared to Iranians and Spaniards. As a conclusion, our study corroborated the validity and reliability of MESSi across three different countries with different geographical and cultural characteristics.

Sociosexuality, Morningness–Eveningness, and Sleep Duration:

Morningness–eveningness is the preference for different times of day for activity and sleep. Here, we addressed the effects of sleep behavior and morningness–eveningness on sociosexuality. Three hundred students (M age = 22.75 years, with 95% between 18 and 28) participated online, answering questions about morningness–eveningness (rMEQ [Reduced Morningness–Eveningness Questionnaire]), midpoint of sleep on free days (MSF), sleep duration, and the Sociosexuality Orientation Inventory–Revised (SOI-R). The SOI-R contains three subscales, Behavior, Attitude, and Desire. Evening orientation and short sleep duration were related to a higher total SOI-R and to the three subscales. Based on the linear models, the strongest effect on sociosexuality was produced by gender (27% explained variance) while age accounted for 6% of variance. Nonadditive variance explained by sleep–wake behavior was 7% (MSF), 4% (sleep duration), and 4% (rMEQ scores; 3% rMEQ-based typology). Older age was related to less-restricted sociosexuality, and men were less restricted than women in Attitude and Desire. Sleep duration and rMEQ scores were associated with Attitude and Desire; but only MSF was significantly related to Behavior. The data show that sleep–wake variables are associated with sociosexuality, with evening orientation and shorter sleep duration being related to a less-restricted sociosexuality.

Conscientiousness but not agreeableness mediates females' tendency toward being a morning person

Individuals differ in their chronotype, and some are identified as morning ones and others as evening ones. Earlier studies showed that women were higher on morningness, conscientiousness, and agreeableness. In this study, we aimed at exploring the mediational effects of conscientiousness and agreeableness in the relationship of gender and morningness-eveningness. Participants were 669 university students. Results supported positive relationships between morningness and conscientiousness and agreeableness and between conscientiousness and agreeableness. Females were higher on all these three variables. Mediation analyses suggested that the effect of gender (here females) on chronotype (here morningness) was mediated by conscientiousness but not agreeableness so that after the mediation partially occurred, the genders effect did not remain significant anymore. This study backed our hypothesis that conscientiousness might play a more pronounced role than the intrinsic diurnal rhythm concerning the sex differences in chronotype.

Sleep timing is linked to sociosexuality: Evidence from German, Polish, Slovak, and Spanish females:

Given the known relationship between eveningness and sociosexuality among females, the aims of this study were: (a) to analyze this relationship in four countries using midsleep time on free days and morning affect measures of morningness–eveningness and (b) to test the role of dark personality and other relevant control variables in this relationship. Data from 1483 females were collected from Poland, Spain, Germany, and Slovakia. Adjusting for age, relationship status, country, age at first intercourse, and Dark Triad traits, the most universal findings were that females with later sleep timing were less sociosexually restricted (3% shared variance with sociosexuality). Sleep timing played a greater role in sociosexuality compared to morning affect. This finding showed that Dark Triad personality is not involved in association between morningness–eveningness and sociosexuality and it added a value to the importance of sleep–wake habits in mating preferences.

Napping and morningness-eveningness

Abstract Our main aim in this work was to investigate the difference in napping behavior in relation to morningness and eveningness. We assessed morningness, eveningness, habitual sleep-wake times and different measures of napping, namely, start time, end time and duration on both weekdays and weekend days. Napping start time did not differ between weekdays and weekends, but napping ended later on weekends. Morning affect positively and eveningness negatively were related to nap end on weekend, nap duration on weekdays/weekend, average nap duration, and midpoint of napping on free days (MNFc). Nap duration was related to morningness and eveningness, with evening-oriented people napping longer. Midpoint of sleep and midpoint of napping were also positively correlated. Further, longer naps do not seem to compensate for lack of sleep on weekdays. As a conclusion, we identified napping as a correlate of morningness, eveningness and midpoint of sleep.