Emerging Adults Mirror Infants' Emotions and Yawns.

Infants' nonverbal expressions-a broad smile or a sharp cry-are powerful at eliciting reactions. Although parents' reactions to their own infants' expressions are relatively well understood, here we studied whether adults more generally exhibit behavioral and physiological reactions to unfamiliar infants producing various expressions. We recruited U.S. emerging adults (N = 84) prior to parenthood, 18-25 years old, 68% women, ethnically (20% Hispanic/Latino) and racially (7% Asian, 13% Black, 1% Middle Eastern, 70% White, 8% multiracial) diverse. They observed four 80-s audio-video clips of unfamiliar 2- to 6-month-olds crying, smiling, yawning, and sitting calmly (emotionally neutral control). Each compilation video depicted 9 different infants (36 clips total). We found adults mirrored behaviorally and physiologically: more positive facial expressions to infants smiling, and more negative facial expressions and pupil dilation-indicating increases in arousal-to infants crying. Adults also yawned more and had more pupil dilation when observing infants yawning. Together, these findings suggest that even nonparent emerging adults are highly sensitive to unfamiliar infants' expressions, which they naturally "catch" (i.e., behaviorally and physiologically mirror), even without instructions. Such sensitivity may have-over the course of humans' evolutionary history-been selected for, to facilitate adults' processing of preverbal infants' expressions to meet their needs.

Yawning and airway physiology: a scoping review and novel hypothesis.

BACKGROUND AND PURPOSE: Yawning is a stereotypical complex muscular movement and is commonly executed by most vertebrates. In seconds, the entire airway is fully dilated and surrounding muscles are powerfully stretched, most prominently around the pharynx. To date, yawning has been rarely studied, and as of yet there is no consensus on its main function. MATERIAL AND METHODS: To investigate a mechanical airway function for yawning, a literature search was conducted to relate the frequency of yawning and obstructive airway conditions. RESULTS: The results show that changes in obstructive airway conditions and alteration of the frequency of yawning are temporally related. INTERPRETATION: These relationships, however, cannot be interpreted as causal, nor can they be extrapolated to explain the function of yawning. Yet airway management and yawning share many physiological characteristics. We therefore propose a novel hypotheses: yawning plays a significant role in airway physiology by muscle repositioning and widening the airway lumen, thereby securing long-term oxygenation.

Yawn contagion in bonobos: Another group, another story.

In primates, yawn contagion (the yawning response elicited by others' yawn) is variably influenced by individual (e.g., sex, age) and social factors (e.g., familiarity) and possibly linked to interindividual synchronization, coordination, and emotional contagion. Two out of three studies on yawn contagion in bonobos (Pan paniscus), found the presence of the phenomenon with mixed results concerning the effect of familiarity and no replication on its modulating factors. To address this puzzling issue, we recorded all occurrences data on yawn contagion in a captive bonobo group (March-June 2021; 18 individuals; La Vallée des Singes, France). Contrary to chimpanzees and humans, the number of triggering yawns increased contagion, possibly owing to a higher stimulus threshold. This aspect may explain the interindividual variability observed in yawn contagion rates. In subjects under weaning, we did not detect yawn contagion and, as it occurs in certain human cohorts, yawn contagion declined with age, possibly due to reduced sensitivity to others. Females responded more than males and elicited more responses from females when showing sexual swelling. As reproductive females are central in bonobo society, our results support the hypothesis that-as in other Hominini-the most influential sex can influence yawn contagion. The relationship quality (measured via grooming/play) did not affect yawn contagion, possibly due to bonobos' xenophilic nature. Overall, this study confirms the presence of yawn contagion in bonobos and introduces new elements on its modulating factors, pointing toward the necessity of cross-group studies.

Earlier than previously thought: Yawn contagion in preschool children.

Yawning is a primitive and stereotyped motor action involving orofacial, laryngeal, pharyngeal, thoracic and abdominal muscles. Contagious yawning, an involuntarily action induced by viewing or listening to others' yawns, has been demonstrated in human and several non-human species. Previous studies with humans showed that infants and preschool children, socially separated during video experiments, were not infected by others' yawns. Here, we tested the occurrence of yawn contagion in 129 preschool children (ranging from 2.5 to 5.5 years) belonging to five different classes by video recording them in their classrooms during the ordinary school activities. As it occurs in adult humans, children of all ages were infected by others' yawns within the 2 min after the perception of the stimulus. The yawn contagion occurred earlier than previously thought. For children, it appears that the natural social setting is more conducive to yawn contagion than the inherently artificial experimental approach. Moreover, children's gender did not affect the level of contagious yawning. The neural, emotional and behavioural traits of preschool children are probably not sufficiently mature to express variability between boys and girls; nevertheless, children appeared to be already well equipped with the 'neural toolkit' necessary for expressing yawn contagion.

Contagious yawning is not a signal of empathy: no evidence of familiarity, gender or prosociality biases in dogs.

Contagious yawning has been suggested to be a potential signal of empathy in non-human animals. However, few studies have been able to robustly test this claim. Here, we ran a Bayesian multilevel reanalysis of six studies of contagious yawning in dogs. This provided robust support for claims that contagious yawning is present in dogs, but found no evidence that dogs display either a familiarity or gender bias in contagious yawning, two predictions made by the contagious yawning-empathy hypothesis. Furthermore, in an experiment testing the prosociality bias, a novel prediction of the contagious yawning-empathy hypothesis, dogs did not yawn more in response to a prosocial demonstrator than to an antisocial demonstrator. As such, these strands of evidence suggest that contagious yawning, although present in dogs, is not mediated by empathetic mechanisms. This calls into question claims that contagious yawning is a signal of empathy in mammals.

Emotional contagion in children with autism spectrum disorder varies with stimulus familiarity and task instructions.

Although deficits in cognitive empathy are well established in individuals with autism spectrum disorder (ASD), the literature on emotional empathy, or emotional contagion, in individuals with ASD is sparse and contradictory. The authors tested susceptibility to contagious yawning and laughter in children with ASD (n = 60) and typically developing (TD) children (n = 60), ages 5-17 years, under various conditions, to elucidate factors that may affect emotional contagion in these populations. Although TD children showed equal amounts of emotional contagion across conditions, children with ASD were highly influenced by the familiarity of the target stimulus, as well as task instructions that encourage eye gaze to target. More specifically, children with ASD exhibited less contagious yawning and laughter than their TD peers except when their attention was explicitly directed to the eyes or (and even more so) when their parents served as the stimulus targets. The authors explore the implications of these findings for theories about the mechanisms underlying empathic deficits in ASD as well as the clinical implications of having parents involved in treatment.

An Adaptive Face Tracker with Application in Yawning Detection.

In this work, we propose an adaptive face tracking scheme that compensates for possible face tracking errors during its operation. The proposed scheme is equipped with a tracking divergence estimate, which allows to detect early and minimize the face tracking errors, so the tracked face is not missed indefinitely. When the estimated face tracking error increases, a resyncing mechanism based on Constrained Local Models (CLM) is activated to reduce the tracking errors by re-estimating the tracked facial features' locations (e.g., facial landmarks). To improve the Constrained Local Model (CLM) feature search mechanism, a Weighted-CLM (W-CLM) is proposed and used in resyncing. The performance of the proposed face tracking method is evaluated in the challenging context of driver monitoring using yawning detection and talking video datasets. Furthermore, an improvement in a yawning detection scheme is proposed. Experiments suggest that our proposed face tracking scheme can obtain a better performance than comparable state-of-the-art face tracking methods and can be successfully applied in yawning detection.

Yawning induced by focal electrical stimulation in the human brain.

The primary function of yawning is not fully understood. We report a case in which electrical stimulation of the putamen in the human brain consistently elicited yawning. A 46-year-old woman with intractable epilepsy had invasive depth electrode monitoring and cortical stimulation mapping as part of her presurgical epilepsy evaluation. The first two contacts of a depth electrode that was intended to sample the left insula were in contact with the putamen. Stimulation of these contacts at 6mA and 8mA consistently elicited yawning on two separate days. Engagement in arithmetic and motor tasks during stimulation did not result in yawning. When considering the role of the putamen in motor control and its extensive connectivity to cortical and brainstem regions, our findings suggest that it plays a key role in the execution of motor movements necessitated by yawning. Furthermore, given the role of the anterior insula in attention and focused tasks, activation of this area while engaged in arithmetic and motor tasks could inhibit the putaminal processing necessary for yawning. Many have hypothesized the function of yawning; however, it remains debatable whether yawning serves a primarily physiological or communicative function or perhaps both.

Oral Behaviors and Parafunctions: Comparison of Temporomandibular Dysfunction Patients and Controls.

The aim of this study is to evaluate the frequency of oral behaviors in patients with temporomandibular disorders (TMD) and a control group without TMD.In this baseline case-control study, 260 controls and 260 subjects with TMD completed the oral behaviors checklist defined as a "self-report scale for identifying and quantifying the frequency of jaw overuse behavior" and underwent clinical examinations using the DC/TMJ international examination form (version May 12, 2013). Relationships of oral parafunctions' frequencies between groups were examined. The statistical analysis was performed with IBM SPSS Statistics 23 software.Age and gender distribution in the study groups did not reveal statistical differences (P > 0.05). Multivariate logistic regression analysis was conducted to establish system of independent oral behaviors for prognosis TMD. The stepwise regression analysis demonstrated that very frequent expression of holding, tightening, or tense muscles is associated with 10.83 times (P < 0.05) higher risk of TMD, grinding teeth together during waking hours with 4.94 times (P < 0.05) higher risk, and sustained talking with 2.64 times (P < 0.05) higher risk of TMD. By contrast, it was determined that 3 oral behaviors were less common in the TMD patients compared with the control group: clenching teeth together during waking hours, facing grimaces, and yawning (P < 0.05). The individuals with TMD reported a significantly higher frequency of 10 behaviors (P < 0.05), 3 of which may be regarded as independent risk factors for TMD. In addition, 3 oral behaviors were more frequently observed in the healthy subjects than in the TMD patients.

Self-reported oral behaviour habits in hyperdivergent and normodivergent facial types.

The relationship between facial morphology and jaw function remains controversial. The purpose of this study was to investigate differences in self-reported oral behaviour habits between individuals with normodivergent and hyperdivergent facial types. Some 80 cases and controls were individually matched on age, sex ethnicity and treatment stage. The participants were recruited from an orthodontic clinic, and included both adolescents and adults. Habitual oral activity was assessed using the Oral Behaviour Checklist (OBC) based on their experiences in the past 4 weeks. Univariate and bivariate analyses were performed. The sample had a mean age of 17·2 years (SD = 4·6; range = 12-49 years), and was predominantly female (65·0%) and of New Zealand European origin (91·3%). The prevalence of reporting one or more frequently performed habitual muscular behaviour in either study group was over 85% (P > 0·05). There was no difference in total OBC score between the hyperdivergent (25·6; SD: 9·0) and normodivergent group (25·3; SD: 9·9). Moreover, there was no difference in the prevalence of either nocturnal or daytime oral behaviours between the two groups. While this study did not include any objective measures of functional or habitual activity, we found no differences in self-reported oral behaviour habits between normodivergent and hyperdivergent individuals. The findings do not support an association between vertical facial form and habitual muscular activity.

Premonitory symptoms in migraine: A cross-sectional study in 2714 persons.

AIM: To describe the frequency and number of premonitory symptoms (PS) in migraine, the co-occurrence of different PS, and their association with migraine-related factors. METHODS: In this cross-sectional study, a validated questionnaire was sent to Finnish migraine families between 2002 and 2013 to obtain data on 14 predefined PS, migraine diagnoses, demographic factors, and migraine characteristics. The estimated response rate was 80%. RESULTS: Out of 2714 persons, 2223 were diagnosed with migraine. Among these, 77% reported PS, with a mean number of 3.0 symptoms compared to 30% (p < 0.001) and 0.5 symptoms (p < 0.001) among 491 persons with non-migraine headaches. Yawning was the most commonly reported symptom (34%) among migraineurs. Females reported PS more frequently than males (81 versus 64%, p < 0.001) and experienced a higher number of different symptoms (mean 3.3 versus 1.8, p < 0.001). All measures of migraine severity were associated with a higher burden of PS. Light and sound sensitivity showed the highest co-occurrence (kappa = 0.51, 95% CI 0.47-0.55). In a generalized linear model, age, gender, higher frequency, duration and intensity of headache, reduced working capacity, most aura symptoms, and associated symptoms of the headache phase were significantly associated with an increased in the number of PS. CONCLUSION: PS are experienced by a majority of migraineurs. More severe migraine is associated with a higher burden of PS. Since the material was not entirely representative of the general population of migraineurs, caution should be exercised in generalizing the results.

Yawn duration predicts brain weight and cortical neuron number in mammals.

Research indicates that the motor action pattern of yawning functions to promote cortical arousal and state change through enhanced intracranial circulation and brain cooling. Because the magnitude of this response likely corresponds to the degree of neurophysiological change, we hypothesized that interspecies variation in yawn duration would correlate with underlying neurological differences. Using openly accessible data, we show that both the mean and variance in yawn duration are robust predictors of mammalian brain weight and cortical neuron number (ρ-values > 0.9). Consistent with these effects, primates tend to have longer and more variable yawn durations compared with other mammals. Although yawning has long been considered a stereotyped action pattern, these findings reveal substantial variation in this response and highlight the importance of measuring yawn duration in future research.

Investigating determinants of yawning in the domestic (Equus caballus) and Przewalski (Equus ferus przewalskii) horses.

Yawning is rare in herbivores which therefore may be an interesting group to disentangle the potential function(s) of yawning behaviour. Horses provide the opportunity to compare not only animals living in different conditions but also wild versus domestic species. Here, we tested three hypotheses by observing both domestic and Przewalski horses living in semi-natural conditions: (i) that domestic horses may show an elevated rate of yawning as a result of the domestication process (or as a result of life conditions), (ii) that individuals experiencing a higher level of social stress would yawn more than individuals with lower social stress and (iii) that males would yawn more often than females. The study involved 19 Przewalski horses (PHs) and 16 domestic horses (DHs) of different breeds living in large outdoor enclosures. The results showed that there was no difference between the PH and DH in yawning frequency (YF). PHs exhibited much higher levels of social interactions than DHs. There was a positive correlation between yawning frequency and aggressive behaviours in PHs, especially males, supporting the idea that yawning may be associated with more excitatory/stressful social situations. A correlation was found between yawning frequency and affiliative behaviours in DHs, which supports the potential relationship between yawning and social context. Finally, the entire males, but not castrated males, showed much higher levels of yawning than females in both species. The intensity (rather than the valence) of the interaction may be important in triggering yawning, which could therefore be a displacement activity that helps reduce tension.

Electrophysiological association of spontaneous yawning and swallowing.

Yawning and swallowing are fundamental physiological processes that are present from fetal stages throughout life and that involve sequential motor activities in the oropharyngo-larynx making it likely that they may share neuroanatomical pathways. We postulate that yawning and swallowing are controlled by a distributed network of brainstem regions including the central pattern generator of swallowing, and therefore spontaneous swallowing is frequently associated with spontaneous yawning. In this study, we sought to test this hypothesis by evaluating the elementary features of yawning in the facial, masseter and submental muscles, together with laryngeal movement sensor and respiratory recordings for spontaneous swallowing. We investigated 15 healthy, normal control subjects, 10 patients with Parkinson's disease (PD) and 10 patients with brainstem stroke (BSS). Apart from four subjects with PD and two with BSS, who had dysphagia, none of the other study subjects were dysphagic by published criteria. Twenty-five subjects (10 control, 10 BSS, 5 PD) were evaluated by 1-h polygraphic recording, and 10 (5 control, 5 PD) underwent whole-night sleep recordings. One hundred thirty-two yawns were collected, 113 of which were associated with spontaneous swallows, a clear excess of what would be considered as coincidence. The yawns related with swallows could be classified into the following three categories. The characteristics or the duration of swallows and yawns were similar between controls and disease subjects, with the exception of increased duration of yawning in subjects with BSS. Our findings support the presence of common neuroanatomico-physiological pathways for spontaneous swallows and yawning.

Yawning in depression: worth looking into.

Yawning often occurs during states of increased sleep propensity. Depression is associated with sleep problems and tiredness. The aim of this paper is to review the present knowledge about possible changes of yawning during an episode of major depression (MD) and to report data on yawning from an online depression forum comprising of 450,000 postings. A literature search did not reveal any study about yawning in people with MD when compared to controls. However, there is evidence for an increased frequency of yawning under the influence of antidepressants. Analysis of the depression forum postings revealed 63 people writing about increased yawning in the context of depression. However, all but one of them were treated with antidepressants; and yawning was not reported as a symptom of depression, but in most cases (N=56) as occurring as a result of treatment with antidepressants. These findings are in agreement with a tonic hyperarousal in typical depression which is reduced by all standard antidepressants. For clinicians, it would be of interest to know whether yawning is reduced in untreated depression and whether it predicts treatment outcome.

Testing yawning hypotheses in wild populations of two strepsirrhine species: Propithecus verreauxi and Lemur catta.

Yawning, although easily recognized, is difficult to explain. Traditional explanations stressed physiological mechanisms, but more recently, behavioral processes have received increasing attention. This is the first study to test a range of hypotheses on yawning in wild primate populations. We studied two sympatric strepsirrhine species, Lemur catta, and Propithecus verreauxi, of the Ankoba forest (24.99°S, 46.29°E, Berenty reserve) in southern Madagascar. Sexual dimorphism is lacking in both species. However, their differences in ecological and behavioral characteristics facilitate comparative tests of hypotheses on yawning. Our results show that within each species males and females yawned with similar frequencies supporting the Dimorphism Hypothesis, which predicts that low sexual dimorphism leads to little inter-sexual differences in yawning. In support of the State Changing Hypothesis yawning frequencies was linked to the sleep-wake cycle and punctuated transitions from one behavior to another. Accordingly, yawning frequencies were significantly higher in L. catta than in P. verreauxi, because L. catta has a higher basal level of activity and consequently a higher number of behavioral transitions. In agreement with the Anxiety Hypothesis, yawning increased significantly in the 10 min following predatory attacks or aggression. Our findings provide the first empirical evidence of a direct connection between anxiety and yawning in lemurs. Our results show that yawning in these two strepsirrhines occurs in different contexts, but more research will be necessary to determine if yawns are a single, unitary behavior.

Importance of yawning in the evaluation of excessive daytime sleepiness: a prospective clinical study.

As a dark and not fully understood side of human nature, yawning is believed to be a signs of various physiological or pathological behaviors of human. In this study, we aimed to investigate the importance of yawning in the evaluation of sleepiness. One hundred and twenty-nine snorers who were suspected to have obstructive sleep apnea syndrome underwent polysomnography and were asked to fill the Epworth sleepiness scale. The number of yawnings of patients was counted during the day following polysomnography. Patients were stratified into two groups: those have apnea hypopnea index <5 (n = 43, group 1) and those have apnea hypopnea index >30 (n = 86, group 2). Mean duration of sleep phases, oxygen saturations, sleep efficacies, yawning frequencies and Epworth scores of the groups were compared. Correlations of yawning frequency with Epworth scores, duration of sleep phases and mean oxygen saturations were investigated. Sleep efficacies were similar between the groups (p > 0.05). Yawning frequencies in group 1 and group 2 were 43.48 and 75.76 (mean rank), respectively (p < 0.01). Mean N1, N2, N3 phase durations and oxygen saturations were significantly lower in group 2 (p < 0.01). While there was a negative correlation between yawning frequency and duration of the non-REM phases and mean oxygen saturation (r = -0.53 and r = -0.31, respectively, p < 0.05), yawning frequency was positively correlated with Epworth scores (r = 0.46, p < 0.05). In addition to the shortened phases of sleep, increased Epworth score and decreased oxygen saturation, increased yawning frequency may indicate sleep deprivation.

Chimpanzees empathize with group mates and humans, but not with baboons or unfamiliar chimpanzees.

Human empathy can extend to strangers and even other species, but it is unknown whether non-humans are similarly broad in their empathic responses. We explored the breadth and flexibility of empathy in chimpanzees, a close relative of humans. We used contagious yawning to measure involuntary empathy and showed chimpanzees videos of familiar humans, unfamiliar humans and gelada baboons (an unfamiliar species). We tested whether each class of stimuli elicited contagion by comparing the effect of yawn and control videos. After including previous data on the response to ingroup and outgroup chimpanzees, we found that familiar and unfamiliar humans elicited contagion equal to that of ingroup chimpanzees. Gelada baboons did not elicit contagion, and the response to them was equal to that of outgroup chimpanzees. However, the chimpanzees watched the outgroup chimpanzee videos more than any other. The combination of high interest and low contagion may stem from hostility towards unfamiliar chimpanzees, which may interfere with an empathic response. Overall, chimpanzees showed flexibility in that they formed an empathic connection with a different species, including unknown members of that species. These results imply that human empathic flexibility is shared with related species.