Love is commonly hypothesized to function as an evolved commitment device, disincentivizing the pursuit of romantic alternatives and signaling this motivational shift to a partner. Here, we test this possibility against a novel signaling-to-alternatives account, in which love instead operates by dissuading alternatives from pursuing oneself. Overall, we find stronger support for the latter account. In Studies 1 and 2, we find that partner quality relative to alternatives positively predicts feelings of love, and love fails to mitigate the negative effects of desirable alternatives on relationship satisfaction—contradicting the classic commitment device account. In Study 3, using a longitudinal design, we replicate these effects and find that changes in partner quality relative to alternatives predict changes in love over time. In Study 4, we replicate the relationship between love and relative partner quality across 44 countries. In Study 5, we find a nearly one-to-one correspondence between the extent to which partner-directed actions are diagnostic of love and reductions in romantic alternatives' attraction to the actor. These results suggest that love may not act as a commitment device in the classic sense by disincentivizing the pursuit of alternatives but by disincentivizing alternatives from pursuing oneself.

Shift work disrupts sleep patterns and is linked to adverse health outcomes, yet the role of chronotype in modulating shift workers' sleep behavior remains underexplored. A field study was conducted with 85 shift workers from an industrial plant in Montevideo, Uruguay, operating under a slow, counterclockwise three-shift rotation system. The abbreviated Munich Chronotype Questionnaire was used to assess sleep timing, duration, and napping behavior across shifts, and chronotype. Sleep duration on workdays was significantly shorter during morning (4.9±0.8h) and night shifts (5.0±1.5h) compared to afternoon shifts (7.9±1.3h). Napping was more frequent during the morning (54.1%) and night shifts (52.9%), contributing to almost an additional hour of sleep to mitigate sleep debt. Evening-oriented workers demonstrated greater sleep flexibility and adaptability, sleeping longer on days off and during night and afternoon shifts: A 1-hour delay in chronotype associated with 7-25 minutes of additional sleep. Morning-oriented workers adapted better to advancing sleep during morning shifts and got more sleep. These results highlight the importance of considering individual chronotypes when designing shift schedules. Personalized shift schedules could enhance sleep health and mitigate the adverse effects of shift work.

Psychological studies on close relationships have often overlooked cultural diversity, dynamic processes, and potentially universal principles that shape intimate partnerships. To address the limited generalizability of previous research and advance our understanding of romantic love experiences, mate preferences, and physical attractiveness, we conducted a large-scale cross-cultural survey study on these topics. A total of 404 researchers collected data in 45 languages from April to August 2021, involving 117,293 participants from 175 countries. Aside from standard demographic questions, the survey included valuable information on variables relevant to romantic relationships: intimate, passionate, and committed love within romantic relationships, physical-attractiveness enhancing behaviors, gender equality endorsement, collectivistic attitudes, personal history of pathogenic diseases, relationship quality, jealousy, personal involvement in sexual and/or emotional infidelity, relational mobility, mate preferences, and acceptance of sugar relationships. The resulting dataset provides a rich resource for investigating patterns within, and associations across, a broad range of variables relevant to romantic relationships, with extensive opportunities to analyze individual experiences worldwide.

Healthy sleep is defined by the combination of adequate duration, good quality, and regular timing. In children, sleep thus depends on the interplay of individual, parental, organizational, community, and social variables, but only a few studies have addressed this issue in a comprehensive way nationwide. Using the Uruguayan nationally representative survey (Nutrition, Child Development, and Health Survey, Encuesta de Nutrición, Desarrollo Infantil y Salud, ENDIS), we present the first epidemiological characterization of chronobiological and sleep parameters in Latin American children. On average, Uruguayan urban children (n = 2437; 5−10-years old) showed quite late chronotypes (MSFsc = 03:53 ± 1:07), moderate misalignment (SJL = 1.0 ± 0.9 h), and adequate sleep duration (SDweek = 9.9 ± 1.0 h). Further, we show the substantial influence of school shift schedules on children's circadian typology and sleep patterns. Our results show that children attending the morning school shift have a higher risk of sleep problems than afternoon-school shift ones. The chronotype and sleep were earlier in morning-school shift children than in children attending the afternoon school shift. However, morning-school shift children had stronger misalignment, shorter sleep on school days, and a higher risk of chronic sleep deficit and non-healthy circadian misalignment (even worse in late chronotypes) than afternoon-shift children. This evidence points to the need of evaluating policies to reorganize school start times to prevent the negative effects that early schooling seems to have on children's sleep health, which has been neglected so far.

Environmental, social, and behavioral variables influence sleep timing and duration. Using wrist-worn accelerometers, we recorded 31 dancers (age = 22.6 ± 3.5) for 17 days and who trained either in the morning (n = 15) or in the late evening (n = 16). We estimated the dancers’ daily sleep pattern: onset, end, and duration. In addition, their minutes of moderate-to-vigorous physical activity (MVPA) and mean light illuminance were also calculated daily and for the morning-shift and late-evening-shift time windows. On training days, the shifts involved differences in sleep timing, alarm-driven waking frequency, and the pattern of light exposure and MVPA duration. Sleep was strongly advanced when dancers trained in the morning and when alarms were used, while morning light had a low influence. Sleep was delayed when dancers were more exposed to light and displayed longer MVPA during the late evening. Sleep duration was strongly reduced on weekends and when alarms were used. A small reduction in sleep duration was also observed when morning illuminance was lower or when late evening MVPA was longer. Training in shifts influenced the timing of environmental and behavioral factors, which added up to shape dancers’ sleep timing and duration.

Recent cross-cultural and neuro-hormonal investigations have suggested that love is a near universal phenomenon that has a biological background. Therefore, the remaining important question is not whether love exists worldwide but which cultural, social, or environmental factors influence experiences and expressions of love. In the present study, we explored whether countries' modernization indexes are related to love experiences measured by three subscales (passion, intimacy, commitment) of the Triangular Love Scale. Analyzing data from 9474 individuals from 45 countries, we tested for relationships with country-level predictors, namely, modernization proxies (i.e., Human Development Index, World Modernization Index, Gender Inequality Index), collectivism, and average annual temperatures. We found that mean levels of love (especially intimacy) were higher in countries with higher modernization proxies, collectivism, and average annual temperatures. In conclusion, our results grant some support to the hypothesis that modernization processes might influence love experiences.

INTRODUCTION Early school start times adversely influence adolescents' sleep duration. Late school start times and remote learning are associated with longer sleep durations. We leveraged a highly variable school schedule adopted after the first SARS-CoV-2 wave in Uruguay to study the influence of a hybrid mode of instruction (in-person/remote) with irregular school start times on adolescents' sleep. METHODS Objective sleep on school nights (120 observations) was determined using accelerometry recordings of 15 high-school students (3 males 15-17 years old). We used mixed-effects regressions to explore the influence of the mode of instruction (in-person/remote) and school start time on adolescents' sleep patterns (onset, end, and duration). RESULTS An irregular individual regime of 2-6 school days per week, either in-person or remote, and with irregular start times (range: 07:30-12:00) were observed during the studied period. Remote learning delayed sleep end by 48 ± 9 min and increased sleep duration by 36 ± 12 min. In addition, 1 h delay in school start time delayed sleep end in 36 ± 4 min and increased sleep duration in 34 ± 5 min. CONCLUSIONS A strong linear association of the mode of instruction and the school start time with participants' sleep was observed: Only waking time was associated with both school start time and mode of instruction, and sleep duration increased when students were taught remotely and when school started later. These results add evidence to the effectiveness of delaying school start time to improve adolescents' sleep. However, these efforts may not overcome the influence of a very late circadian orientation, as observed in Uruguayan adolescents.

Morningness/Eveningness (M/E) is an attribute related to adolescent mental and physical health. The Morningness/Eveningness Scale for Children (MESC) is a widely used instrument for measuring M/E in adolescents. In this study, an Spanish translation of the MESC was adapted to the Rio de la Plata population. A psychometric study was carried out in a sample of 368 Uruguayan adolescents (63.6% females), between 15 and 18 years old, who attended to either a morning (7:30 AM to 11:30 AM) or an afternoon school shift (11:30 AM to 3:30 PM). The scale showed good reliability (Cronbach's alpha = 0.74), high temporal stability (r = 0.86, p < 0.001), good concurrent validity with mid-sleep point (r = -0.42, p < 0.001), and a two-factor solution. No difference in scores was observed between sexes or age groups. However, scores were different between school shifts, which proved to be a useful tool to study social influences on the circadian preferences. This study shows that MESC is a reliable and valid instrument for M/E assessment in adolescents, but social pressures should be considered when employing this score.

People across the world and throughout history have gone to great lengths to enhance their physical appearance. Evolutionary psychologists and ethologists have largely attempted to explain this phenomenon via mating preferences and strategies. Here, we test one of the most popular evolutionary hypotheses for beauty-enhancing behaviors, drawn from mating market and parasite stress perspectives, in a large cross-cultural sample. We also test hypotheses drawn from other influential and non-mutually exclusive theoretical frameworks, from biosocial role theory to a cultural media perspective. Survey data from 93,158 human participants across 93 countries provide evidence that behaviors such as applying makeup or using other cosmetics, hair grooming, clothing style, caring for body hygiene, and exercising or following a specific diet for the specific purpose of improving ones physical attractiveness, are universal. Indeed, 99% of participants reported spending >10 min a day performing beauty-enhancing behaviors. The results largely support evolutionary hypotheses: more time was spent enhancing beauty by women (almost 4 h a day, on average) than by men (3.6 h a day), by the youngest participants (and contrary to predictions, also the oldest), by those with a relatively more severe history of infectious diseases, and by participants currently dating compared to those in established relationships. The strongest predictor of attractiveness-enhancing behaviors was social media usage. Other predictors, in order of effect size, included adhering to traditional gender roles, residing in countries with less gender equality, considering oneself as highly attractive or, conversely, highly unattractive, TV watching time, higher socioeconomic status, right-wing political beliefs, a lower level of education, and personal individualistic attitudes. This study provides novel insight into universal beauty-enhancing behaviors by unifying evolutionary theory with several other complementary perspectives.

Sleep is crucial for college students’ well-being. Although recommended sleep duration is between 7-9 hours per day, many students do not sleep that much. Scholar demands are among the causes of observed sleep deprivation in youth. We explored the influence of having a school test on previous night sleep in first-year students and the association of sleep duration and test performance. We ran two surveys in freshman students of the Universidad de la República, Montevideo, Uruguay: 1) 97 students of the School of Sciences who took the test at the same time; and 2) 252 School of Psychology students who took the test in four successive shifts. More than 1/2 of the participants (survey #1) and almost 1/3 (survey #2) reported short regular sleep duration (< 7h). In both samples, the sleep duration of the night before the test was reduced with respect to regular nights (survey #1: 2.1 ± 0.2 h, p < 0.001; survey #2: between 1.7 ± 0.4 h and 3.6 ± 0.3 h, all p < 0.001), with more than 10% of the students who did not sleep at all. In survey 2, sleep duration increased in later shifts (F (3,248) = 4.6, p = 0.004). Using logit regressions, we confirmed that sleep duration was positively related to test scores in both samples (survey #1: exp B = 1.15, p < 0.001; pseudo-R2 = 0.38; survey #2: exp B = 1.03, p < 0.001; pseudo-R2 = 0.25). Delaying test start time may prevent the reduction in sleep duration, which may also improve school performance. In addition, educational policies should include information for students about the impact of sleep on learning and of the consequences of reduced sleep duration.

Fear of animals is an important issue to consider in order to increase knowledge about nature and foster positive attitudes for nature conservation. Spiders are a challenging group, because they are widely feared and disliked by humans, although the majority of species are harmless and they play a positive role in natural ecosystems. By means of self-report questionnaires filled out before and after three different extracurricular educational experiences, we examined how knowledge, fear perception and attitudes towards spiders changed in Uruguayan children 10-11 years old. Experience groups were (1) short experience ('Spider-single-lesson group'), children receiving 1 h of information and brief interaction with spiders; (2) no experience ('Control-single-lesson group'), children receiving 1 h of information on another topic (no interaction with spiders); (3) long experience ('Spider-multiple-lesson group'), children receiving 40 h of information and several interactions with spiders. We found that children's knowledge improved in both groups gaining spider experience. Further, more children reported positive attitudes towards spiders, especially in the Spider-multiple-lesson group. Our findings highlight the importance of hands-on and extended activities to correct false concepts about unpopular animals and foster positive attitudes towards nature conservation.

Sleep behaviour is controlled by both circadian and homeostatic influences. Changes in both factors are related to the delayed sleep timing observed in adolescence, which also generates restrictions in their sleep duration. In addition, the circadian factor explains part of the observed influence of light on sleep duration. We recorded 15 high-school students for 23 days (vacation: 11 days; school term: 12 days) using GENEactive accelerometers. We employed a repeated-measures analysis to explore the day-to-day bidirectional association between mean light exposure and sleep behaviour across a period with extreme variability in social pressures. Sleep onset was more than 30 min earlier and sleep duration almost 20 min longer when previous day light was 10 times more intense. Light intensity had a reduction of more than 20% as sleep ended 1 hr later. Besides, sleep onset and offset were both later during vacation than on school days (almost 2 hr and 4 hr, respectively) and free days (almost 1 hr, respectively). Therefore, sleep duration was almost 2 hr longer on vacation and free days than on school days. On the other hand, light exposure intensity was twice as high during vacation days when adjusted by sleep timing. Insufficient sleep duration is a major problem for adolescents. Although we found that light exposure was associated with longer sleep duration, the influence of school start times was greater and ended up prevailing, which explained the short sleep durations observed on school days.

A wide range of literature connects sex ratio and mating behaviours in non-human animals. However, research examining sex ratio and human mating is limited in scope. Prior work has examined the relationship between sex ratio and desire for short-term, uncommitted mating as well as outcomes such as marriage and divorce rates. Less empirical attention has been directed towards the relationship between sex ratio and mate preferences, despite the importance of mate preferences in the human mating literature. To address this gap, we examined sex ratio's relationship to the variation in preferences for attractiveness, resources, kindness, intelligence and health in a long-term mate across 45 countries (n = 14 487). We predicted that mate preferences would vary according to relative power of choice on the mating market, with increased power derived from having relatively few competitors and numerous potential mates. We found that each sex tended to report more demanding preferences for attractiveness and resources where the opposite sex was abundant, compared to where the opposite sex was scarce. This pattern dovetails with those found for mating strategies in humans and mate preferences across species, highlighting the importance of sex ratio for understanding variation in human mate preferences.

Background: There is increasing evidence defining reading competency in terms of accuracy, speed and prosody, as well as interest in gaining better understanding of the interrelation as a function of prosodic features. This study aims to analyze the relationship between reading competency, in terms of accuracy and speed of written word recognition, and two attributes related to prosody in oral reading of texts: speech rate and rhythm. Method: Oral reading of a narrative text by 141 third and fourth grade Spanish-speaking students was analyzed using an automated acoustic speech procedure and their reading competency was assessed. Results: Reading proficiency was associated with a lower proportion of the number and duration of pauses and greater regularity of syllable intervals, resulting in a higher rate of speech and higher regularity of rhythm. The reading experience improves rhythmic reading with some independence from the levels of automation achieved in written word recognition. Conclusions: The results suggest that when there is greater reading competence there is greater speed and rhythmic expressiveness; this improves with reading experience when a sufficient level of automation has been achieved in reading access.

Considerable research has examined human mate preferences across cultures, finding universal sex differences in preferences for attractiveness and resources as well as sources of systematic cultural variation. Two competing perspectives—an evolutionary psychological perspective and a biosocial role perspective—offer alternative explanations for these findings. However, the original data on which each perspective relies are decades old, and the literature is fraught with conflicting methods, analyses, results, and conclusions. Using a new 45-country sample ( N = 14,399), we attempted to replicate classic studies and test both the evolutionary and biosocial role perspectives. Support for universal sex differences in preferences remains robust: Men, more than women, prefer attractive, young mates, and women, more than men, prefer older mates with financial prospects. Cross-culturally, both sexes have mates closer to their own ages as gender equality increases. Beyond age of partner, neither pathogen prevalence nor gender equality robustly predicted sex differences or preferences across countries.