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Handling stress initially inhibits, but then potentiates yawning in budgerigars (Melopsittacus undulatus)
Abstract
In mammals, yawning is associated with social and physiological stress, as well as thermoregulation, but little is known about why yawning occurs in stressful contexts or how it is integrated with natural stressors. To investigate the stress sensitivity of yawning in birds, we exposed budgerigars (Melopsittacus undulatus) to a handling stressor that simulated a predatory encounter. Each bird was captured, gently held for 4 min, and then released and videotaped for 1 h (experimental). On a separate day (±24 h), the undisturbed animal was videotaped for 1 h (control). The relationship between handling-induced yawning and body temperature was assessed in a separate experiment, in which the underwing temperatures of the same birds were measured at 1 min intervals during a 4 min holding period. After handling stress, yawning frequency was initially suppressed, then sharply increased within 20 min. Underwing temperature increased during handling, and individuals’ final temperatures at minute 4 were negatively correlated with their latencies to yawn after handling. Thus, stress-induced hyperthermia may be responsible for associations between yawns and stress. These results indicate that yawning may offer a sensitive, noninvasive measure of stress in birds.
... To date, only in budgerigars (Melopsittacus undulatus) is there experimental evidence that yawning is related to stress in a nonmammalian vertebrate (Miller, Gallup, Vogel, & Clark, 2010). In that study, handling of a bird simulated capture by a predator, and, after release, behavioral responses were measured over three 20min time blocks (Miller et al., 2010). ...
... To date, only in budgerigars (Melopsittacus undulatus) is there experimental evidence that yawning is related to stress in a nonmammalian vertebrate (Miller, Gallup, Vogel, & Clark, 2010). In that study, handling of a bird simulated capture by a predator, and, after release, behavioral responses were measured over three 20min time blocks (Miller et al., 2010). In comparison to control periods, yawning was delayed and infrequent in the first 20 min following release but then significantly increased in frequency during the next 20 min-a temporal pattern similar to that described in rodents (see Moyaho & Valencia, 2002). ...
... From this, we determined, for each bird, the latencies to perform each behavior and the latency to move (either laterally while perched or by initiating flight), following both conditions. As in the study of handling stress (Miller et al., 2010) we also broke the hour into three 20-min time blocks to test for a change in the temporal pattern of these behaviors following the stimulus. For statistical tests, analyses of variance (ANOVAs) were used to compare latencies or frequencies of a given behavior between conditions. ...
Yawning may serve both social and nonsocial functions. When budgerigars (Melopsittacus undulatus) are briefly held, simulating capture by a predator, the temporal pattern of yawning changes. When this species is observed in a naturalistic setting (undisturbed flock), yawning and also stretching, a related behavior, are mildly contagious. On the basis of these findings, we hypothesized that a stressful event would be followed by the clustering of these behaviors in a group of birds, which may be facilitated both by a standard pattern of responding to a startling stressor and also contagion. In this study, we measured yawning and stretching in 4-bird groups following a nonspecific stressor (loud white noise) for a period of 1 hr, determining whether auditory disturbances alter the timing and frequency of these behaviors. Our results show that stretching, and to a lesser degree yawning, were nonrandomly clumped in time following the auditory disturbances, indicating that the temporal clustering is sensitive to, and enhanced by, environmental stressors while in small groups. No decrease in yawning such as found after handling stress was observed immediately after the loud noise but a similar increase in yawning 20 min after was observed. Future research is required to tease apart the roles of behavioral contagion and a time-setting effect following a startle in this species. This research is of interest because of the potential role that temporal clumping of yawning and stretching could play in both the collective detection of, and response to, local disturbances or predation threats.
... We studied Nazca boobies in a large breeding colony at Punta Cevallos, Isla Española, Galápagos Islands, Ecuador (1°23′S, 89°37′W), the site of our long-term research on this species [6] between [19][20][21][22][23][24][25][26][27][28][29][30] March 2012, the middle of the annual breeding season. ...
... We conducted a standardized capture-restraint test for analysis of the HPA axis stress response (see [18] for details) on 12 adults (seven non-breeders, five breeders), using only males to control any sex effect. A sex effect is not expected for birds, based on the limited evidence available [17,28]. For each "During Test" bird, an initial blood sample of 1 cm 3 was taken within 3 min of initial disturbance (mean time ± SD = 2.17 ± 0.38 min) to avoid the confounding effect of capture on baseline [CORT] [38]. ...
... Nestlings also showed an inhibition/potentiation cycle: despite probable hyperthermia, 18 of 27 (0.67) nestlings visited by NAVs showed a latency to yawn of at least 1 min after assuming a normal posture that would permit gular flutter (Fig. 4). In a study with a similar design, budgerigars (Melopsittacus undulatus) given a capturerestraint test suppressed yawning during the first 20 min after release, then increased yawning in the next 20 min, and finally returned to a control level 40-60 min after release [28]. Noting a correlation between yawning and body temperature in their experiment, Miller et al. [28] suggested that yawning has a thermoregulatory function. ...
Yawning is a familiar and phylogenetically widespread phenomenon, but no consensus exists regarding its functional significance. We tested the hypothesis that yawning communicates to others a transition from a state of physiological and/or psychological arousal (for example, due to action of a stressor) to a more relaxed state. This arousal reduction hypothesis predicts little yawning during arousal and more yawning (above baseline) during and after down-regulation of arousal. Experimental capture-restraint tests with wild adult Nazca boobies (Sula granti), a seabird, increased yawning frequency after release from restraint, but yawning was almost absent during tests. Natural maltreatment by non-parental adults also increased yawning by nestlings, but only after the maltreatment ended and the adult left. CORT (corticosterone) was a logical a priori element of the stress response affecting the stressor-yawning relationship under the arousal reduction hypothesis, and cannot be excluded as such for adults in capture-restraint tests but is apparently unimportant for nestlings being maltreated by adults. The arousal reduction hypothesis unites formerly disparate results on yawning: its socially contagious nature in some taxa, its clear pharmacological connection to the stress response, and its temporal linkage to transitions in arousal between consciousness and sleep.
... During yawning, expansion of the pharynx can quadruple its diameter, and the larynx opens with maximal abduction of the vocal cords (Walusinski, 2006). Animals other than humans yawn, with yawning having various functions including social reactions when encountering another individual visually or physically [Siamese fighting fish (Betta splendens): Baenninger, 1987]; starvation or preparation for feeding [Herman's tortoises (Testudo hermanni) and European pond turtles (Emys orbicularis) : Luttenberger, 1973 and Red Hills salamanders (Phaeognathus hubrichti): Bakkegard, 2017]; stress reactions from being handled by a researcher or encountering a predator [budgerigars (Melopsittacus undulatus): Miller et al., 2010]; and resting [ostrich (Struthio camelus australis): Sauer and Sauer, 1967]. In terrestrial mammals, yawning occurs during resting states, and the frequency of occurrence changes throughout the day, especially in association with fixed feeding times [lions (Panthera leo) and mandrills (Papio sphinx) : Baenninger, 1987]. ...
... To the best of our knowledge, this is the first study to examine underwater open-mouth behaviors that might be classified as yawning in dolphins. The yawning action of the mouth has been widely identified among various vertebrates (e.g., Sauer and Sauer, 1967;Luttenberger, 1973;Baenninger, 1987;Miller et al., 2010;Bakkegard, 2017) but has yet to be confirmed in a fully aquatic mammal. ...
... The function of yawning in animals varies, including social reactions when encountering another individual (Siamese fighting fish: Baenninger, 1987), starvation or preparation for feeding (Herman's tortoises and European pond turtles: Luttenberger, 1973, Red Hills salamanders: Bakkegard, 2017, and lions and mandrills: Baenninger, 1987; stress reactions from being handled by a researcher or encountering a predator (budgerigars: Miller et al., 2010); and resting (ostrich: Sauer and Sauer, 1967, this study). Although the contexts of yawning are different, the behavioral form of yawning (slow gaping and quick closure) is similar among various vertebrates, suggesting a stereotyped action pattern (Gallup et al., 2016). ...
Yawning is an involuntary action that begins with a slow opening of the mouth with inhalation, followed by a maximum gaping phase, and ends with a short exhalation and the closing of the mouth. A wide variety of vertebrate species, including humans, yawn. Here, we report underwater yawn-like behavior in three captive common bottlenose dolphins, inferred from 119-h of observations. Five cases of yawn-like behavior were selected out of 2045 open-mouth behaviors, after removing intentional open-mouth behaviors. Yawn-like behaviors were chosen that had a mouth open–close duration ratio of ≤ 1 (duration of Phase 3, the period of mouth closing after maximum opening, divided by the duration of Phase 1, the period of mouth opening from start to maximum opening). Naïve human evaluators selected “yawn-like” behaviors. All five cases of yawn-like behavior occurred during inactive periods, similar to human yawns. In three of the five cases, inactivity levels significantly decreased within 4 min after the yawn-like behavior; therefore, yawn-like behavior in dolphins may increase their arousal level in drowsy states. Thus, the yawn-like behavior of dolphins, without breathing, is similar to yawning in terrestrial animals, including humans.
... Laboratory studies on birds and mammals showed that yawning frequency initially decreases or remains unchanged in the first 20-min following a stressful event. As the effect of the anxiogenic events clears, yawning generally increases in a 20-40 min time window [Miller et al., 2010;Miller et al., 2012;Moyaho & Valencia, 2002]. In primates there are only anecdotal reports on the possible linkage between stressors and "tension yawns." ...
... We started a PD all occurrences observation on yawning, lasting 60 min on the study subject, if one of the previously described disturbing conditions was satisfied. The few available studies [Rattus norvegicus; Moyaho & Valencia, 2002;Melopsittacus undulatus;Miller et al., 2010;Sula granti, Liang et al., 2015] showed that the yawning response to stressful stimuli does not necessarily increase in the first 10 min but it can increase after 20 and/or 40 min. Therefore, the 1hour PD observation considered in this study was divided into 3 blocks (0-10 min, 10-20 min, 20-60 min). ...
... Both Lemur catta and Propithecus verreauxi yawned within 10 minutes of exposure to a disturbing event (Prediction 3 supported). This finding contrasts with literature on non-primates showing a 20-40 min delayed yawning response to stressful stimuli, such as isolation [Sula granti, Liang et al., 2015], confinement and handling [Melopsittacus undulatus;Miller et al., 2010] and electric shocks [Rattus norvegicus; Moyaho & Valencia, 2002]. In these studies, the delayed response is explained through the Arousal Reduction Hypothesis, predicting that yawning is elicited by arousal reduction, when the animal starts relaxing. ...
... In a series of experiments designed to induce thermal stress in captive budgerigars (Melosittacus undulatus), increases in yawning were reliably produced by rapid rises in ambient temperature within a thermal chamber ( Gallup et al. 2009. The pattern of yawning has also been measured in this species following a 4-min handling stressor, which simulates a predator encounter and produces a significant physiological stressor as measured by rises in body temperature ( Miller et al. 2010). Within this study it was shown that, in comparison to a control condition, handling significantly modulated the temporal expression of yawning following the encounter ( Miller et al. 2010). ...
... The pattern of yawning has also been measured in this species following a 4-min handling stressor, which simulates a predator encounter and produces a significant physiological stressor as measured by rises in body temperature ( Miller et al. 2010). Within this study it was shown that, in comparison to a control condition, handling significantly modulated the temporal expression of yawning following the encounter ( Miller et al. 2010). In particular, yawns were initially inhibited after release (~1.5 yawns/h), but were then potentiated 20-40-min thereafter (>5 yawns/h). ...
... Accordingly, the CPT has been shown to not only increase a biomarker ( Banks et al. 2014) and peripheral measures of autonomic arousal ( Schwabe et al. 2008), but to also increase cortisol levels with peak activity occurring after a delay (≥10 min post-stress) ( Alomari et al. 2015;Schwabe et al. 2008;Viena et al. 2012). Consistent with previously documented temporal effects following physical stressors in horses (Fenner et al. 2016), rats (Moyaho and Valencia 2002) and birds ( Miller et al. 2010Miller et al. , 2012Liang et al. 2015), we hypothesized that yawning would increase following the CPT, but only in the delayed condition. Because yawning has been documented to be relatively infrequent among participants in laboratory research ( Baenninger and Greco 1991), contagious yawning was used as a proxy for spontaneous yawning in this experiment. ...
A growing number of studies on non-human animals have documented that stressors modulate the expression of yawning. In particular, recent experimental research shows that yawns are initially inhibited following physical stress, but then become potentiated thereafter. However, stress-induced yawning in humans has yet to be demonstrated experimentally. Here, we investigated the temporal relationship between self-reported contagious yawning and an acute physical stressor in 141 human subjects in the laboratory. Using a 2 × 2 between-subjects design, participants either underwent the cold pressor test (CPT) or a matched control condition prior to viewing a contagious yawning stimulus that was either displayed immediately thereafter or following a 20-min delay. Consistent with the comparative literature, we show an interaction between stress and time conditions, whereby both the incidence and frequency of yawning are lowest in the immediate-CPT trials and highest in the delayed-CPT trials. These findings support a homologous effect of acute physical stress on yawning across birds and mammals that may be related to an adaptive thermoregulatory and arousal function.
... These hypotheses can be classified into two groups, the physiological and social hypotheses. In the former group, yawning is posited to act as a homeostatic restoring mechanism, and, with the intensification of the studies, some of these hypotheses such as brain cooling, anxiety and drowsiness hypothesis have found an increasing support 3,4,[8][9][10][11][12][13][14] . In the latter group, the performance of yawning is posited to express the emotional state of the yawner as a communicative tool (e.g., threat yawns), since other members of the group would be able to associate it with certain contexts or behaviours and so could act accordingly 12-15 . ...
... For example, in chimpanzees, Baker and Aureli 27 showed that individuals tended to yawn and self-scratch more frequently during high social tension conditions that provoked an increase of anxiety and arousal in the subjects. Recent findings suggest a possible effect of yawning as a stress-releaser, which helps restoring physiological/emotional homeostasis 4,28,29 . ...
... If yawning and self-scratching are behavioural responses linked to an anxiety state of South American sea lions in response of an immediate perturbing event 4,22 (the Social Distress Hypothesis), we expect that after an agonistic event, these two behavioural patterns will increase by following a similar trend in both the aggressor and the victim (Prediction 3). ...
Spontaneous yawning is a widespread behaviour in vertebrates. However, data on marine mammals are scarce. In this study, we tested some hypotheses on the functions of yawning in a captive group of South American sea lions (Otaria flavescens). According to the Dimorphism Hypothesis, species showing low levels of sexual dimorphism in canine size do not show sex differences in yawning distribution; this was supported by our findings, since yawning did not differ between the sexes. Yawning was more frequently performed during resting/sleeping contexts, thus supporting the Drowsiness Hypothesis. Yawning and self-scratching are considered reliable indicators of short-term anxiety in sea lions, since they immediately increased after conflicts both in aggressors and victims (Social Distress Hypothesis supported). In the long-term, yawning was not correlated with individuals’ dominance status, thus showing that anxiety is similarly experienced by dominants and subordinates. The last two findings can be explained by the social competition of this species, that involves individuals independently from their sex, age or ranking status. Therefore, the exposure to frequent stressful events can induce similar levels of anxiety in all the subjects (Resource Inequity Hypothesis supported). In conclusion, spontaneous yawning in sea lions seems to share similar functions with other social mammals, suggesting that this behaviour is a possible plesiomorphic trait.
... More recent research suggests that a primary function of yawning is to enhance intracranial circulation (Walusinski, 2014), which, in turn, could promote arousal and state change (Provine, 1986;Baenninger, 1997;Provine, 2005) via brain cooling (Gallup & Gallup, 2007;. In support of this view, yawns tend to cluster around major transitions of activity (Baenninger, Binkley, & Baenninger, 1996), important daily events (Baenninger 1987), and stressful situations and stimuli (Miller, Gallup, Vogel, & Clark, 2010;Eldakar, Tartar, Garcia, Ramirez, Dauzonne & Gallup, 2017). Moreover, yawns are linked with indicators of neurophysiological arousal (Sato-Suzuki, Kita, Oguri, & Arita, 1998;Sato-Suzuki, Kita, Seki, Oguri, & Arita, 2002;Seki, Nakatani, Kita, Sato-Suzuki, Oguri, & Arita, 2003;Kasuya, Murakami, Oshima, & Dohi, 2005;Kita, Kubota, Yanagita, & Motoki, 2008; but see Guggisberg, Mathis, Herrmann, & Hess, 2007) and followed by significant decreases in brain and skull temperature (Shoup-Knox, Gallup, Gallup, & McNay, 2010;Equibar, Uribe, Cortes, Bautista, & Gallup, 2017;Gallup, Herron, Militello, Swartwood, Cortes, & Eguibar, 2017). ...
... Moreover, yawns are linked with indicators of neurophysiological arousal (Sato-Suzuki, Kita, Oguri, & Arita, 1998;Sato-Suzuki, Kita, Seki, Oguri, & Arita, 2002;Seki, Nakatani, Kita, Sato-Suzuki, Oguri, & Arita, 2003;Kasuya, Murakami, Oshima, & Dohi, 2005;Kita, Kubota, Yanagita, & Motoki, 2008; but see Guggisberg, Mathis, Herrmann, & Hess, 2007) and followed by significant decreases in brain and skull temperature (Shoup-Knox, Gallup, Gallup, & McNay, 2010;Equibar, Uribe, Cortes, Bautista, & Gallup, 2017;Gallup, Herron, Militello, Swartwood, Cortes, & Eguibar, 2017). Ultimately, these neurovascular changes may improve aspects of cognitive processing (Miller et al., 2010;Miller, Gallup, Vogel, & Clark, 2012). ...
... Contagious yawning was used as a proxy for spontaneous (non-social) yawning since it can be reliably induced within the laboratory (Provine, 1986;Platek, Critton, Myers, & Gallup, 2003). Moreover, recent studies have repeatedly shown that variables controlling the expression of spontaneous yawning also alter contagious yawning in the same fashion (Gallup & Gallup, 2007;Massen, Dusch, Eldakar, & Gallup, 2014;Eldakar, Dauzonne, Prilutzkaya, Garcia, Thadal, & Gallup, 2015;Eldakar et al., 2017). ...
... Laboratory studies on birds and mammals showed that yawning frequency initially decreases or remains unchanged in the first 20-min following a stressful event. As the effect of the anxiogenic events clears, yawning generally increases in a 20-40 min time window [Miller et al., 2010;Miller et al., 2012;Moyaho & Valencia, 2002]. In primates there are only anecdotal reports on the possible linkage between stressors and "tension yawns." ...
... We started a PD all occurrences observation on yawning, lasting 60 min on the study subject, if one of the previously described disturbing conditions was satisfied. The few available studies [Rattus norvegicus; Moyaho & Valencia, 2002;Melopsittacus undulatus;Miller et al., 2010;Sula granti, Liang et al., 2015] showed that the yawning response to stressful stimuli does not necessarily increase in the first 10 min but it can increase after 20 and/or 40 min. Therefore, the 1hour PD observation considered in this study was divided into 3 blocks (0-10 min, 10-20 min, 20-60 min). ...
... Both Lemur catta and Propithecus verreauxi yawned within 10 minutes of exposure to a disturbing event (Prediction 3 supported). This finding contrasts with literature on non-primates showing a 20-40 min delayed yawning response to stressful stimuli, such as isolation [Sula granti, Liang et al., 2015], confinement and handling [Melopsittacus undulatus;Miller et al., 2010] and electric shocks [Rattus norvegicus; Moyaho & Valencia, 2002]. In these studies, the delayed response is explained through the Arousal Reduction Hypothesis, predicting that yawning is elicited by arousal reduction, when the animal starts relaxing. ...
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. Am. J. Primatol. © 2015 Wiley Periodicals, Inc.
© 2015 Wiley Periodicals, Inc.
... These birds served as an appropriate non-mammalian model to explore this relationship because much is known about their naturalistic and experimentally-induced yawn frequency, [31][32][33] and yawning has previously been implicated in thermoregulation in this species. 17,34 Following a similar methodology to Eguibar et al., 26 thermographic images were continuously captured at 10 second intervals to track immediate shifts in facial temperature before and after yawns. In addition, based on previous research showing a strong correlation between body temperature and yawning following stress within this species, 34 correlations were run to assess the relationship between both yawn latency and frequency and the maximum facial temperature measured across the trials. ...
... 17,34 Following a similar methodology to Eguibar et al., 26 thermographic images were continuously captured at 10 second intervals to track immediate shifts in facial temperature before and after yawns. In addition, based on previous research showing a strong correlation between body temperature and yawning following stress within this species, 34 correlations were run to assess the relationship between both yawn latency and frequency and the maximum facial temperature measured across the trials. ...
... Correlations were also run to assess the linear relationships between yawn latency (i.e., time to first yawn, in minutes, following the first image captured) and frequency with the maximum facial temperature recorded during each trial. Based on previous research linking yawning with body temperature in this species following a prolonged handling restraint, 34 it was hypothesized that birds with higher facial temperature would yawn sooner and more frequently across the experiment. Due to a small sample size, a Kendall's tau non-parametric correlation was used (one-tailed test). ...
Accumulating comparative and interdisciplinary research supports a brain cooling function to yawning. In particular, previous research has shown significant decreases in both brain and skull temperature following yawning in mammals. In a recent study using a thermal imaging camera, significant reductions in both the cornea and concha temperature were observed following yawns in the high-yawning subline of Sprague-Dawley rats. Here, we performed a similar experiment to investigate shifts in facial temperature surrounding yawning in an avian species with more typical yawning patterns: budgerigars (Melopsittacus undulatus). In particular, we took maximal surface temperature recordings from the face (cere or eye) from 13 birds over a one-hour period to track changes before and after yawns. Similar to previous findings in high-yawning rats, we identified significant cooling (-0.36oC) of the face 10-20-seconds following yawning in budgerigars. Consistent with the hypothesis that yawns serve a thermoregulatory function, facial temperatures were slightly elevated just prior to yawning and then decreased significantly below baseline levels immediately thereafter. Similarly, birds that yawned during the trials had consistently higher facial temperatures compared to those that did not yawn. Moreover, yawn latency and overall yawn frequency were strongly correlated with the highest facial temperature recorded from each bird across trials. These results provide convergent evidence in support of a brain cooling function to yawning, and further validate the use of thermal imaging to monitor changes in skull temperature surrounding yawning events.
... Yawning in humans has been found to be associated with transitions in arousal level [24] and is thought to be a thermoregulatory mechanism that cools the brain after periods of stress [25]. In budgerigars, handling stress inhibits yawning initially prior to an eventual increase [26]. Miller et al [26] also reported that the budgerigars with higher skin temperatures (namely those that had been most distressed), yawned sooner than others, which may also be reflected in the results of the current study ( Fig 9). ...
... In budgerigars, handling stress inhibits yawning initially prior to an eventual increase [26]. Miller et al [26] also reported that the budgerigars with higher skin temperatures (namely those that had been most distressed), yawned sooner than others, which may also be reflected in the results of the current study ( Fig 9). Horses in this experiment were not physically active or required to engage in cognitively demanding activities whilst undergoing observation. ...
Restrictive nosebands are common in equestrian sport. This is concerning, as recent evidence suggests that very tight nosebands can cause a physiological stress response, and may compromise welfare. The objective of the current study was to investigate relationships that noseband tightness has with oral behavior and with physiological changes that indicate a stress response, such as increases in eye temperature (measured with infrared thermography) and heart rate and decreases in heart rate variability (HRV). Horses (n = 12) wearing a double bridle and crank noseband, as is common in dressage at elite levels, were randomly assigned to four treatments: unfastened noseband (UN), conventional area under noseband (CAUN) with two fingers of space available under the noseband, half conventional area under noseband (HCAUN) with one finger of space under the noseband, and no area under the noseband (NAUN). During the tightest treatment (NAUN), horse heart rate increased (P = 0.003), HRV decreased (P < 0.001), and eye temperature increased (P = 0.011) compared with baseline readings, indicating a physiological stress response. The behavioral results suggest some effects from bits alone but the chief findings are the physiological readings that reflect responses to the nosebands at their tightest. Chewing decreased during the HCAUN (P < 0.001) and NAUN (P < 0.001) treatments. Yawning rates were negligible in all treatments. Similarly, licking was eliminated by the NAUN treatment. Following the removal of the noseband and double bridle during the recovery session, yawning (P = 0.015), swallowing (P = 0.003), and licking (P < 0.001) significantly increased compared with baseline, indicating a post-inhibitory rebound response. This suggests a rise in motivation to perform these behaviors and implies that their inhibition may place horses in a state of deprivation. It is evident that a very tight noseband can cause physiological stress responses and inhibit the expression of oral behaviors.
... Interestingly, both ASD and the prevalence of psychopathic traits are more common among males 46,47 . These populations are also of interest to study with regards to the hypothesized functional significance of yawn contagion in promoting collective vigilance and synchronized group behavior/ movement [48][49][50][51][52][53] . Impairments in imitation and joint attention among individuals with ASD diminish cooperation and coordinated actions 54 . ...
... Thus, the reduced tendency to yawn contagiously among individuals scoring high in psychopathic traits could reflect a generalized impairment in biobehavioral synchrony. Moreover, it has been theorized that contagious yawning evolved to enhance collective vigilance 48,49 and coordinate or synchronize group behavior [50][51][52][53] , and these functional accounts for yawn contagion can explain the negative association between contagious yawning and psychopathy in the absence of emotional contagion. For example, groups characterized by higher levels of psychopathy have previously been shown to have more dysfunctional interactions and lower levels of cohesion 60 . ...
Considerable variation exists in the contagiousness of yawning, and numerous studies have been conducted to investigate the proximate mechanisms involved in this response. Yet, findings within the psychological literature are mixed, with many studies conducted on relatively small and homogeneous samples. Here, we aimed to replicate and extend upon research suggesting a negative relationship between psychopathic traits and yawn contagion in community samples. In the largest study of contagious yawning to date (N = 458), which included both university students and community members from across 50 nationalities, participants completed an online study in which they self-reported on their yawn contagion to a video stimulus and completed four measures of psychopathy: the primary and secondary psychopathy scales from the Levenson Self-Report Psychopathy Scale (LSRPS), the psychopathy construct from the Dirty Dozen, and the Psychopathic Personality Traits Scale (PPTS). Results support previous findings in that participants that yawned contagiously tended to score lower on the combined and primary measures of psychopathy. That said, tiredness was the strongest predictor across all models. These findings align with functional accounts of spontaneous and contagious yawning and a generalized impairment in overall patterns of behavioral contagion and biobehavioral synchrony among people high in psychopathic traits.
... Accordingly, we did not observe any behavioral mechanisms for T b -stabilization, such as panting or yawning (e.g. [24,41]), after the stressor. The T b change reported here is greater than that in previous studies, despite comparable stressor duration. ...
... However, contrary to our predictions, T b remained stable in indoor birds during handling (Fig. 2). This suggests that stressinduced hyperthermia may not be an integral part of the acute stress response in chickadees; a finding that contrasts with several other studies on birds [8,12,21,22,27,41,55]. However, the largest stressinduced change in eye-region skin temperature (− 1.4°C) in the closely related blue tit (Cyanistes caeruleus) was observed within 15 s of the (non-contact) stressor, after which temperature approached baseline levels within a few min [31]. ...
... accumulating (Greco et al., 1993). For instance, yawning is associated with fatigue in humans (Zilli et al., 2008) and birds (Sauer and Sauer, 1967), movement in humans (Baenninger et al., 1996) and primates (Vick and Paukner, 2010), stress in rodents (Moyaho and Valencia, 2002) and birds (Miller et al., 2010), and boredom in humans (Provine, 1986b). Recent comparative research also supports a role of yawning in brain thermoregulation (e.g., Gallup and Gallup, 2007;Gallup, 2008;Gallup and Hack, 2011;Gallup and Eldakar, 2011;Shoup-Knox et al., 2010), and it has been suggested that the cooling component of yawning may facilitate arousal by reinstating optimal brain temperature. ...
... A camcorder, which continuously recorded picture and audio, was placed inside the aviary, positioned at the corner diagonally across from two large perches, allowing a view of the entire flock except during feeding and flying. Due to recent research showing that certain environmental manipulations influence yawning in budgerigars (Gallup et al., 2009;Miller et al., 2010), we controlled for factors such as time, temperature and relative humidity. Furthermore, the audio track from the camcorder was used to confirm that there were no external disturbances (e.g., someone entering the room) influencing the pattern of behaviors. ...
Yawning is contagious in humans and some non-human primates. If there are social functions to contagious behaviors, such as yawning, they might occur in other highly social vertebrates. To investigate this possibility, we conducted an observational study of yawning and an associated behavior, stretching, in budgerigars (Melopsittacus undulatus), a social, flock-living parrot. Flock-housed budgerigars were videotaped for 1.5h at three time-blocks during the day (early morning, afternoon and early evening), and the times of all yawns and stretches for each bird were recorded. Both yawning and stretching were temporally clumped within sessions, but were uniformly distributed across the trials of a particular time-block. This suggests that clumping was not a result of circadian patterning and that both behaviors could be contagious. There was additional evidence of contagion in stretching, which occurred in two forms - a posterior-dorsal extension of either one foot or both feet. Birds that could have observed a conspecific stretch, and that then stretched themselves within 20s, replicated the form of the earlier stretch significantly more often than expected by chance. This study provides the first detailed description of temporal patterns of yawning under social conditions in a flock-living species as well as the first support for contagious yawning and stretching in a non-primate species in a natural context. Experimental evidence will be necessary to confirm the extent of contagion in either behavior.
... Moreover, several additional lines of evidence indicate that yawning is an adaptation rather than a byproduct. For example, yawning is an overt response that conflicts with other movement (Miller et al. 2010) and in rare cases can entail extreme costs resulting in subluxation or locking of the jaw (Tesfaye and Lal 1990). In addition, psychological research shows hedonic properties to yawning (Provine and Hamernik 1986) where the inability to achieve full yawns is often perceived as frustrating (Walusinski 2018). ...
... More recently, Liang et al. (2015) coined this the arousal reduction hypothesis, proposing that yawns signal to others that an individual is experiencing a down regulation of arousal and vigilance. In a study of stressful encounters in wild Nazca boobies (Sula granti), these authors showed that, similar to research on budgerigars (Melopsittacus undulatus) (Miller et al. 2010(Miller et al. , 2012b and humans (Eldakar et al. 2017), yawning is absent during exposure to stressors but then becomes potentiated thereafter. These findings were interpreted by Liang et al. as support for the arousal reduction hypothesis, with yawning "communicating to others the transition from a state of physiological and/or psychological arousal (for example, due to action of a stressor) to a more relaxed state" (p. ...
While the origin of yawning appears to be physiologic, yawns may also hold a derived communicative function in social species. In particular, the arousal reduction hypothesis states that yawning signals to others that the actor is experiencing a down regulation of arousal and vigilance. If true, seeing another individual yawn might enhance the vigilance of observers to compensate for the reduced mental processing of the yawner. This was tested in humans by assessing how exposure to yawning stimuli alters performance on visual search tasks for detecting snakes (a threatening stimulus) and frogs (a neutral stimulus). In a repeated-measures design, 38 participants completed these tasks separately after viewing yawning and control videos. Eye-tracking was used to measure detection latency and distractor fixation frequency. Replicating previous evolutionary-based research, snakes were detected more rapidly than frogs across trials. Moreover, consistent with the view that yawning holds a distinct signaling function, there were significant interactions for both detection latency and distractor fixation frequency showing that vigilance was selectively enhanced following exposure to yawns. That is, after viewing videos of other people yawning, participants detected snakes more rapidly and were less likely to fixate on distractor frogs during trials. These findings provide the first experimental evidence for a social function to yawning in any species, and imply the presence of a previously unidentified psychological adaptation for preserving group vigilance.
... Yawning or yawn-like behavior has been observed not only in humans but also in various vertebrate taxa, including mammals (Carnivora and Primates; Baenninger 1987), birds (Struthioniformes; Sauer and Sauer 1967), reptiles (Testudines;Luttenberger 1975), amphibians (Caudata; Bakkegard 2017), and fish (Perciformes; Rasa 1971). Yawning or yawn-like behavior is considered to serve physiological purposes (e.g., promoting arousal or vigilance, humans; Baenninger 1997; mammals other than humans; Rossman et al. 2017;amphibians;Bakkegard 2017;state-change, mammals;Baenninger 1987;reptiles;Luttenberger 1975;drowsiness, human;Zilli et al. 2008; mammals other than humans ;Deputte 1994;birds;Sauer and Sauer 1967, changing temperature, humans;Gallup and Gallup 2007; mammals other than humans; Gallup et al. 2011;birds;Gallup et al. 2010), and social functions (e.g., an individual communicates his or her emotional state, human; Provine 1986; conflict, mammals other than humans; Deputte 1994;Palagi et al. 2019;bird;Miller et al. 2010;Miller et al. 2012;fish;Baenninger 1987). In particular, the drowsiness hypothesis has received increasing support from observational and experimental studies (Guggisberg et al. 2010). ...
... In addition, behavioral studies of yawning in other vertebrates, such as birds, amphibians, and fish, should be conducted because of insufficient information on the behavioral context of yawning among these taxa. Finally, we need to study yawning in the vertebrates whose yawning is unknown, such as Mammalia (such as Monotremata, Xenarthra, Hyracoidea, Afroinsectiphilia, Marsupialia, Chiroptera, Scandentia, Dermoptera, Glires, Eulipotyphla, Pholidota), Aves (except for budgerigars and ostrich; Sauer and Sauer 1967;Gallup et al. 2009;Miller et al. 2010Miller et al. , 2012, Reptilia (except European pond turtles and Herman's tortoise ;Luttenberger 1975), Amphibia (except for Red Hills salamander and Eastern hellbender; Bakkegard 2017; Hartzell et al. 2017), and Pisces (except for Siamese fighting fish and yellow damsel fish; Rasa 1971;Baenninger 1987). The method used in this study would be useful to research yawning in animals in which the context is unknown. ...
Yawning is an involuntary action that occurs in three phases: (1) slow mouth opening accompanied by inhalation, (2) maintaining the maximum mouth size, and (3) quick closure with exhalation. Yawning is a phylogenetically widespread behavior in vertebrates. Here, we report yawn-like behavior in a captive dugong. Fourteen yawn-like behaviors were identified in a 20.1 h observation period. These yawn-like behaviors occurred significantly more during resting states than during more active states. These yawn-like behaviors of the dugong may function as yawns, typically associated with drowsiness. These findings imply that yawning may be a universal behavior, even in fully aquatic mammals.
... Results show that yawning was preceded in all instances by rapid increases in brain temperature, with correspondingly consistent decreases in brain temperature and a return to baseline after each yawn. In accord with these findings, recent research has shown that under-wing body temperature of budgerigars is negatively correlated with yawn latency (i.e., hyperthermic birds yawn sooner) following handling stress [23]. Furthermore, a number of studies have now documented either a positive or curvilinear relationship between ambient temperature and yawning frequency, including reports on birds [14,15], rats [24] and primates [25,26]. ...
The function of the paranasal sinuses has been a controversial subject since the time of Galen, with many different theories advanced about their biological significance. For one, the paranasal sinuses have been regarded as warmers of respiratory air, when in actuality these structures appear to function in cooling the blood. In fact, human paranasal sinuses have been shown to have higher volumes in individuals living in warmer climates, and thus may be considered radiators of the brain. The literature suggests that the transfer of cool venous blood from the paranasal sinuses to the dura mater may provide a mechanism for the convection process of cooling produced by the evaporation of mucus within human sinuses. In turn, the dura mater may transmit these temperature changes, initiated by the cool venous blood from the heat-dissipating surfaces of the sinuses, to the cerebrospinal fluid compartments. Furthermore, it has recently been demonstrated in cadaveric dissections that the thin bony posterior wall of the maxillary sinus serves as an origin for both medial and lateral pterygoid muscle segments, an anatomic finding that had been previously underappreciated in the literature. The present authors hypothesize that the thin posterior wall of the maxillary sinus may flex during yawning, operating like a bellows pump, actively ventilating the sinus system, and thus facilitating brain cooling. Such a powered ventilation system has not previously been described in humans, although an analogous system has been reported in birds.
... Comparative research from birds, rats, and humans shows that yawning is followed by reductions in brain and body temperature, is suppressed by other methods of behavioral cooling, and is influenced by the direction and range of ambient temperature (reviewed by in press). Consistent with the view that yawning is a thermoregulatory behavior, recent research has revealed a strong negative correlation between body temperature and the latency to yawn following a stressor in budgerigars (Melopsittacus undulatus) (Miller et al., 2010). This hypothesis complements those of arousal and state change, suggesting that the cooling component of yawning may facilitate these processes by reinstating brain thermal homeostasis. ...
Yawning appears to be involved in arousal, state change, and activity across vertebrates. Recent research suggests that yawning may support effective changes in mental state or vigilance through cerebral cooling. To further investigate the relationship between yawning, state change, and thermoregulation, 12 Sprague-Dawley rats (Rattus norvegicus) were exposed to a total of two hours of ambient temperature manipulation over a period of 48 hours. Using a repeated measures design, each rat experienced a range of increasing (22→32°C), decreasing (32→22°C), and constant temperatures (22°C; 32°C). Yawning and locomotor activity occurred most frequently during initial changes in temperature, irrespective of direction, compared to more extended periods of temperature manipulation. The rate of yawning also diminished during constant high temperatures (32°C) compared to low temperatures (22°C). Unlike yawning, however, stretching was unaffected by ambient temperature variation. These findings are compared to recent work on budgerigars (Melopsittacus undulatus), and the ecological selective pressures for yawning in challenging thermal environments are discussed. The results support previous comparative research connecting yawning with arousal and state change, and contribute to refining the predictions of the thermoregulatory hypothesis across vertebrates.
... (3) Sleep cycles trigger yawning during distinct changes in brain/body temperature (4) Conditions, drugs, and neurotransmitters affect yawning and temperature in predicted ways* (5) Yawning is inhibited by nasal breathing and forehead cooling* (6) Predicted fluctuations in brain temperature surround yawning events in rodents* (7) Predicted fluctuations in oral temperature surround excessive yawning in humans (8) Hyperthermic birds yawn sooner following handling-stress a (9) Fluctuations in ambient temperature produce predicted changes in yawn frequency* (10) Yawning is reduced when ambient temperatures near or exceed body temperature* *Indicates that a replication of this specific effect has been demonstrated in an independent sample; a Miller et al. (2010). ...
Over the past 5 years numerous reports have confirmed and replicated the specific brain cooling and thermal window predictions derived from the thermoregulatory theory of yawning, and no study has found evidence contrary to these findings. Here we review the comparative research supporting this model of yawning among homeotherms, while highlighting a recent report showing how the expression of contagious yawning in humans is altered by seasonal climate variation. The fact that yawning is constrained to a thermal window of ambient temperature provides unique and compelling support in favor of this theory. Heretofore, no existing alternative hypothesis of yawning can explain these results, which have important implications for understanding the potential functional role of this behavior, both physiologically and socially, in humans and other animals. In discussion we stress the broader applications of this work in clinical settings, and counter the various criticisms of this theory.
... Problems continue to arise with the logic used for the argument that the origin and function of yawning is social or communicative. In the most primitive sense, a signal is a behavior or structure that has evolved to alter the behavior of another organism (Maynard Smith and Harper, 2003). Thus, signals need to be interpreted and recognizable by others, and mechanisms need to be in place to receive these signals. ...
Guggisberg et al. (2010) reviewed the evidence for the origin and function of yawning, and conclude that theories describing a physiological role lack support. Instead, they argue research supports the notion that yawning has a communicative function. Contrary to the authors' claim that the social/communication hypothesis has the "best experimental evidence", there is in fact no definitive experimental support for the predictions of this model. Furthermore, the authors claim to take an evolutionary perspective, but sufficient examples across the comparative (non-primate) literature are missing, and they fail to acknowledge phylogenic history. Due to the ubiquity of this behavior across vertebrates, and the regularity of its occurrence in a number of different physiological states and social contexts, it is likely that instead of serving one purpose, yawning is multifunctional across a number of species. The most parsimonious explanation for the origin of yawning suggests that any social value is a derived feature, while the primitive feature or function is physiological. The current paper addresses these concerns, and identifies a number of other weaknesses in the social/communication hypothesis as a global explanation for the origin and function of yawning.
... Consistent with this theory, research on both rats (Rattus norvegicus) and humans has demonstrated that yawns are surrounded by predicted fluctuations in brain and skull temperature, i.e., yawning is preceded by rises in temperature and followed by decreases in temperature thereafter (humans, rats, ShoupKnox et al. 2010). Furthermore, research on birds (Melopsittacus undulatus) has shown that following stress-induced hyperthermia the latency to yawn is negatively correlated with the peak body temperature ( Miller et al. 2010). Literature from diverse fields of medicine, physiology and pharmacology also support the connection between yawning and brain thermoregulation ( Gallup and Gallup 2008). ...
The thermoregulatory theory posits that yawns function to cool the brain in part due to counter-current heat exchange with the deep inhalation of ambient air. In support of this theory, previous cross-cultural research on humans has shown that self-reported contagious yawning frequency varies between seasons with distinct ambient temperature ranges. However, it remains possible that differences in yawning across seasons are a result of physiological circadian changes across the year rather than variation in ambient temperature. In an attempt to address this question, here we discuss the results of a study investigating the variation in the frequency of self-reported contagious yawning within a restricted range of a single season in one geographic location. A total of 142 pedestrians were recruited outdoors during an 18-day period over the summer in an equatorial monsoon climate in southern Florida, USA. Consistent with the thermoregulatory theory of yawning, results showed that self-reported contagious yawning frequency varied predictably across temperature gradients. This was true after statistically controlling for relative humidity, time of day, time spent outside, testing day, age of participant, and amount of sleep the night before. These findings provide further evidence suggesting a brain cooling function to yawning.
... A combination of experimental and observational studies across a diverse array of mammals and birds have revealed a distinct temporal relationship between the onset of stress and the associated yawning response (Demuru & Palagi, 2012;Eldakar et al., 2017;Fenner et al., 2016;Liang et al., 2015;Miller et al., 2010;Moyaho & Valencia, 2002). For example, in a study of captive budgerigars, yawns were measured over a 1 h period following handling restraint . ...
Yawning is a stereotyped action pattern that is prevalent across vertebrates. While there is growing consensus on the physiological functions of spontaneous yawning in neurovascular circulation and brain cooling, far less is known about how the act of yawning alters the cognition and behaviour of observers. By bridging and synthesizing a wide range of literature, this review attempts to provide a unifying framework for understanding the evolution and elaboration of derived features of yawning in social vertebrates. Recent studies in animal behaviour, psychology and neuroscience now provide evidence that yawns serve as a cue that improves the vigilance of observers, and that contagious yawning functions to synchronize and/or coordinate group activity patterns. These social responses to yawning align with research on the physiological significance of this behaviour, as well as the ubiquitous temporal and contextual variation in yawn frequency across mammals and birds. In addition, these changes in mental processing and behaviour resulting from the detection of yawning in others are consistent with variability in the expression of yawn contagion based on affinity and social status in primates. Topics for further research in these areas are discussed.
... It is characterized by an extensive and involuntary opening of the mouth with deep, prolonged inspirations and short expirations lasting approximately 10 seconds and commonly accompanied by stretching. Yawning has been observed in stressful situations in different species like monkeys [22][23][24][25], rats [26] and birds [27]. Thus, the emergence of yawning as freezing becomes infrequent could mean that animals change the way they manifest their affective response to the distress of others, but that animals are still responsive to the distress of the other. ...
Witnessing of conspecifics in pain has been shown to elicit socially triggered freezing in rodents. It is unknown how robust this response is to repeated exposure to a cage-mate experiencing painful stimulation. To address this question, shock-experienced Observer rats repeatedly witnessed familiar Demonstrators receive painful footshocks (six sessions). Results confirm that Observers freeze during the first testing session. The occurrence of this behaviour however gradually diminished as the experimental sessions progressed, reaching minimal freezing levels by the end of the experiments. In contrast, the appearance and continuous increase in the frequency of yawning, a behavior that was inhibited by metyrapone (i.e,. a glucocorticoid synthesis blocker), might represent an alternative coping strategy, suggesting that the observer's reduced freezing does not necessarily indicate a disappearance in the affective response to the Demonstrator's distress.
... Does arousal explain yawning in boobies? booby nestlings is, however, likely to be individually variable, as reported in a laboratory study of handling stress and yawning in another bird, the budgerigar (Melopsittacus undulatus) (Miller et al., 2010 ). Wide individual variation in budgerigars' underwing temperatures during handling restraint correlated with variation in post-stress timing of yawning, with the more hyperthermic budgerigars yawning sooner after stress. ...
... One interpretation is that yawns are triggered by elevated temperature inside the skull, and that the physiological consequences of yawning discussed above result in temperature reduction. Consistent with this view, heightened core body temperature following handling-stress has been shown to be correlated with earlier onset and higher frequency of yawning in birds [26], and experimental manipulations designed to promote brain cooling have been shown to diminish yawning frequency in humans [7]. Furthermore, a number of medical conditions and drugs affect yawning and brain/core temperature in reciprocal patterns. ...
Background
Yawning is a stereotyped behavior that enhances blood flow to the skull, and the resulting counterflow has been hypothesized as a mechanism for brain cooling. Studies have shown that yawns are strongly associated with physiological and pathological conditions that increase brain temperature, and that they are followed by equivalent decreases in brain temperature. However, measured reductions in cranial or facial temperatures following yawning have yet to be reported, to our knowledge. To accomplish this, we used a subline of Sprague-Dawley rats that yawn at a much greater rate (20 yawns/h) than do outbred Sprague-Dawley rats (2 yawns/h).
Results
Using an infrared camera, we effectively evaluated thermal changes in the cornea and concha of these rats before, during, and after yawns. The maximum temperature in both regions significantly decreased 10 s following yawns (concha: −0.3 °C, cornea: −0.4 °C), with a return to basal temperatures after 20 s.
Conclusions
This study is the first clear demonstration of yawning-induced thermal cooling on the surface of the face, providing convergent evidence that this behavior plays a functional role in thermoregulation. As other studies have demonstrated that yawning is capable of reducing cortical brain temperature, our current data support the idea that yawning functions as a thermoregulator, affecting all structures within the head.
... People who are active, for example, tend to yawn less frequently than those who are less active. Also consistent with the view that yawning produces an arousing effect, yawns are common following stressful events, threats, and increases in anxiety (e.g., Eldakar et al., 2017;Liang et al., 2015;Miller et al., 2010;Miller et al., 2012b). In addition, numerous studies have revealed that yawning is associated with hormonally-induced penile erection (reviewed by Baenninger, 1997), a well-defined indicator of sexual arousal. ...
Various studies and researchers have proposed a link between contagious yawning and empathy, yet the conceptual basis for the proposed connection is not clear and deserves critical evaluation. Therefore, we systematically examined the available empirical evidence addressing this association; i.e., a critical review of studies on inter-individual differences in contagion and self-reported values of empathy, differences in contagion based on familiarity or sex, and differences in contagion among individuals with psychological disorders, as well as developmental research, and brain imaging and neurophysiological studies. In doing so, we reveal a pattern of inconsistent and inconclusive evidence regarding the connection between contagious yawning and empathy. Furthermore, we identify study limitations and confounding variables, such as visual attention and social inhibition. Future research examining links between contagious yawning and empathy requires more rigorous investigation involving objective measurements to explicitly test for this connection.
... They typically sat calmly on the floor and appeared sleepy at the end of the "before" phase preceding the playback. It may be assumed that this sleepiness could have been a consequence of the stress they felt before the beginning of the experiment when handled, as it has been observed in budgerigars (Melopsittacus undulatus) [76]. Stress-related behaviours were mostly exhibited during playback stimulations and, to a lesser extent, after these playbacks. ...
Vocal communication is used across the animal kingdom to transfer information from emitters to receivers, such as size, sex, age, dominance status or even emotional states. The transmission of an emotional state from one individual to another is called “emotional contagion” and is classified as the first level of empathy. Emotional contagion is thought to be stronger between familiar individuals. While affiliation represents a stronger relation between individuals than mere familiarity, it remains understudied whether affiliation modulates emotional reactions as well. Using cockatiels (Nymphicus hollandicus), we played back three types of audio stimuli to individual birds: a partner’s distress call (emitted when birds are caught or forcibly restrained), a non-partner’s distress call, and a control sound (white noise). The calls were recorded from familiar birds with either low (non–partners) or high levels of affiliation (partners). The subjects’ response was scored using four behavioural parameters: the time spent near the loudspeaker, the amount of movements, the number of calls emitted, and the position of the crest. Across all variables, birds were more attentive and active when confronted to distress calls compared to control sounds, particularly when the distress call was emitted from a partner rather than a non-partner. These results raise the possibility that distress calls do not only function as a stimulus-triggering automatic reaction in cockatiels but also transmit emotions. Moreover, affiliation enhanced emotional reactions to conspecific distress calls. Our data provides first insights into the mechanisms of emotional contagion in parrots.
... The extent of body surface temperature changes we observed are within the magnitude of those seen in other bird species subjected to handling [25,29,84]. Immediate drops in body surface temperature (similar to those reported here but longer in duration) were also observed from a variety of alternative measurement sites in both chicken (Gallus gallus domesticus) studies [25,29]. ...
Reactions to acute stressors are critical for survival. Yet, the challenges of assessing underlying physiological processes in the field limit our understanding of how variation in the acute stress response relates to fitness in free-living animals. Glucocorticoid secretion during acute stress can be measured from blood plasma concentrations, but each blood sample can only provide information for one point in time. Also, the number of samples that can be extracted from an individual in the field is usually limited to avoid compromising welfare. This restricts capacity for repeated assessment, and therefore temporal resolution of findings within- and between-acute stress responses - both of which are important for determining links between acute stress and fitness. Acute stress induces additional body surface temperature changes that can be measured non-invasively, and at high frequencies using thermal imaging, offering opportunities to overcome these limitations. But, this method's usefulness in the field depends on the extent that environmental conditions affect the body surface temperature response, which remains poorly understood. We assessed the relative importance of individual physiology (baseline glucocorticoid concentrations) and environmental conditions (air temperature and relative humidity) in determining the eye region surface temperature (Teye) response to acute stress, in wild blue tits (Cyanistes caeruleus) during trapping, handling and blood sampling. When controlling for between-individual baseline variation, Teye initially dropped rapidly below, and then recovered above baseline, before declining more slowly until the end of the test, 160 s after trap closure. One measure of the amplitude of this response - the size of the initial drop in Teye - was dependent on environmental conditions, but not baseline corticosterone. Whereas, two properties defining response dynamics - the timing of the initial drop, and the slope of the subsequent recovery - were related to baseline corticosterone concentrations, independently of environmental conditions. This suggests inferring the acute stress response using thermal imaging of Teye will be practical under fluctuating environmental conditions in the field.
... For example, the affiliation hypothesis might predict that contagious yawning should be seen more frequently during reconciliation periods after conflict while the collective vigilance hypothesis posits that contagious yawning should increase in response to external disturbances [37,86]. However, it is important to note that these theories are not necessarily mutually exclusive [87] and that factors such as stress appear to influence yawning propensity in complex ways [88,89]. Additionally, an important next step is to consider evidence of contagious yawning outside of mammals. ...
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 pro-social 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.
... In accordance with the arousal hypothesis, Baker and Aureli (1997) showed that chimpanzees, Pan troglodytes, yawned more frequently after periods of high social tension that induced arousal in the subjects, and in South American sea lions, yawning peaked immediately after an aggressive conflict in both aggressors and victims . Several studies indicate that, under such circumstances, yawning can function as a stress-releaser mechanism by facilitating physiological/emotional homeostasis (Eldakar et al., 2017;Liang et al., 2015;Miller et al., 2010;Miller, Gallup, Vogel & Clark, 2012;Moyaho et al., 2017;Walusinski, 2006Walusinski, , 2010. ...
Yawning, a fixed action pattern, is widespread in almost all vertebrate taxa. Several hypotheses have been
proposed to explain the functions of yawning. These hypotheses, not mutually exclusive, can be
conventionally arranged according to both physiological (e.g. drowsiness hypothesis: yawning when
switching between sleep and being awake; arousal hypothesis: yawning in contexts of high social tension)
and social communicative domains (e.g. contagion hypothesis, activity synchronization hypothesis).
Owing to their high social cohesion and synchronized group activity, wild lions are a good model to
investigate both spontaneous yawning from the physiological domain and, possibly, contagious yawning,
from the social communicative domain. We videorecorded two groups of lions in the Makalali Reserve
(Limpopo region, South Africa) and analysed their yawning behaviour. Spontaneous yawning was
particularly frequent when the lions were relaxed and, in agreement with the 24 h activity cycle typical
of the species, was similarly distributed over the night and day. These findings support the drowsiness
hypothesis predicting that yawning is linked to the transition between sleeping and waking (and vice
versa). Lions did not show high levels of yawning during competition over clumped food such as carcasses;
hence, the arousal hypothesis was not supported. We found that yawn contagion was present,
supporting the contagion hypothesis and the activity synchronization hypothesis. Our findings suggest
that the convergence of motor behaviour triggered by yawn contagion (to our knowledge never explored
in any other species) could represent an important tool to shed light on the adaptive and immediate
benefits that underlie the evolution of the yawn contagion phenomenon in human and nonhuman
animals.
Research suggests that yawning provides a brain cooling function in homeotherms, and that excessive yawning may be a useful diagnostic indicator of abnormal thermoregulation in humans. Accordingly, the frequency of yawning should increase during instances of hyperthermia, but not fever (i.e., pyrexia), since this represents an elevation in the homeostatic set point rather than thermoregulatory failure. To our knowledge, no research has investigated the association between yawning frequency and fever in humans. Here we present the hypothesis that frequent yawning could be used as an initial signal for fever relief, either through the effectiveness of antipyretics or the natural break of a fever. Applications of this research include the improved behavioral monitoring of patients.
This study examined the impact of rearing environment on the behavioural responses of wild European starlings (Sturnus vulgaris) to standard laboratory husbandry procedures. We compared birds that had been caught from the wild as independent juveniles with birds taken from the nest and hand-reared in the laboratory from approximately ten days post-hatch. Although hand-rearing can increase habituation to humans and hence reduce fearfulness in laboratory birds, in other species maternal deprivation is also associated with increased stress-sensitivity in later life. Thus, the welfare benefits of hand-rearing are unclear. We investigated the interaction between rearing environment (12 hand-reared versus 12 wild-caught birds) and current laboratory housing conditions (enriched versus non-enriched cages and top-level cages versus bottom-level cages) on measures of behaviour before, during and after husbandry. Both wild-caught and hand-reared birds reacted to focal husbandry by moving to the periphery of their cages, indicative of high escape motivation during a stressful procedure. Wild-caught birds were overall less active than hand-reared birds. We found no difference in the response of the wild-caught and hand-reared birds to focal husbandry, but hand-reared birds were faster to resume normal behaviour following husbandry than wild-caught birds when housed in the top cages. We interpret our results as showing evidence for chronic depressive apathy (lower overall activity) coupled with greater fear (longer latencies to resume normal behaviour following husbandry) in the wild-caught birds in some environments. Our data support the conclusion that hand-rearing is associated with some welfare benefits for birds involved in laboratory research.
Yawning behavior was studied in two species of macaques: the long-tailed macaque (Macaca fascicularis) and the Japanese macaque (M. fuscata). Japanese macaques yawned much more than long-tailed macaques. Age, sex, and dominance rank exerted different effects on yawning in the two species. In the long-tailed macaques, sex differences in frequency of yawning emerged only after sexual maturity; yawning rates increased significantly in both males and females as they reached sexual maturity; and, among males, dominance rank was positively correlated with frequency of yawning. Differently, in the Japanese macaques, males, both mature and immature, yawned more than same-aged females; sexual maturity was associated with an increase in yawning in males only; and male rank did not correlate with the frequency of yawning. Regardless of interspecific differences, the overall results supported only in part the finding that, in Old World monkeys, yawning is largely influenced by plasma concentrations of androgens. There was evidence that social factors were also important in influencing the age-sex class distribution of yawning.
To assess the effect of procedures on animal welfare, various physiological parameters, such as body weight, hormone levels in plasma and/or urine, heart rate (HR), blood pressure and body temperature (BT), can be used. When measuring physiological parameters with techniques involving restraint of the animals, the results must be interpreted with caution, since restraint itself may have an effect on those parameters. Radio-telemetry, using an implantable transmitter, provides a way to obtain more accurate and reliable physiological measurements from freely moving animals in their own environment. In this study, we have used radio-telemetry to investigate the influence of conditioning on the increase of HR and BT as provoked by handling of mice. It was found that, after a conditioning period of 12 days, the increase of HR due to handling was significantly reduced.
We conducted two experiments that implicate yawning as a thermoregulatory mechanism. The first experiment demonstrates that different patterns of breathing influence susceptibility to contagious yawning. When participants were not directed how to breathe or were instructed to breathe orally (inhaling and exhaling through their mouth), the incidence of contagious yawning in response to seeing videotapes of people yawning was about 48%. When instructed to breathe nasally (inhaling and exhaling through their nose), no participants exhibited contagious yawning. In a second experiment, applying temperature packs to the forehead also influenced the incidence of contagious yawning. When participants held a warm pack (46°C) or a pack at room temperature to their forehead while watching people yawn, contagious yawning occurred 41% of the time. When participants held a cold pack (4°C) to their forehead, contagious yawning dropped to 9%. These findings suggest that yawning has an adaptive/functional component that it is not merely the derivative of selection for other forms of behavior. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Comparative research suggests that yawning is a thermoregulatory behavior in homeotherms. Our previous experiments revealed that yawning increased in budgerigars (Melopsittacus undulatus) as ambient temperature was raised toward body temperature (22-->34 degrees C). In this study, we identify the range of temperatures that triggers yawning to rule out the possible effect of changing temperature in any range. To corroborate its thermoregulatory function, we also related the incidence of yawning to other avian thermoregulatory behaviors in budgerigars (e.g., panting, wing venting). In a repeated measures design, 16 budgerigars were exposed to 4 separate 10-min periods of changing temperatures: (a) low-increasing (23-->27 degrees C), (b) high-increasing (27-->33 degrees C), (c) high-decreasing (34-->28 degrees C), and (d) low-decreasing (28-->24 degrees C). Birds yawned significantly more during the high-increasing temperature range, and yawning was positively correlated with ambient temperature across trials. Yawning was also positively correlated with other thermoregulatory behaviors. This research clarifies the previously demonstrated relationship between yawning rate and temperature by providing evidence that the physiological trigger for yawning is related to increasing body temperatures rather than the detection of changing external temperatures.
Plasma corticosterone (CORT) measures are a common procedure to detect stress responses in rodents. However, the procedure is invasive and can influence CORT levels, making it less than ideal for monitoring CORT circadian rhythms. In the current paper, we examined the applicability of a non-invasive fecal CORT metabolite measure to assess the circadian rhythm. We compared fecal CORT metabolite levels to circulating CORT levels, and analyzed change in the fecal circadian rhythm following an acute stressor (i.e. blood sampling by tail veil catheter). Fecal and blood samples were collected from male adolescent rats and analyzed for CORT metabolites and circulating CORT respectively. Fecal samples were collected hourly for 24 h before and after blood draw. On average, peak fecal CORT metabolite values occurred 7-9 h after the plasma CORT peak and time-matched fecal CORT values were well correlated with plasma CORT. As a result of the rapid blood draw, fecal production and CORT levels were altered the next day. These results indicate fecal CORT metabolite measures can be used to assess conditions that disrupt the circadian CORT rhythm, and provide a method to measure long-term changes in CORT production. This can benefit research that requires long-term glucocorticoid assessment (e.g. stress mechanisms underlying health).
The authors studied grooming and yawning caused by mild stress in laboratory Sprague-Dawley rats (Rattus norvegicus). Two groups received 3 and 6 sequences of 5 foot shocks at random intervals (RI) and fixed intervals (FI), respectively. A 3rd group was not shocked (NS). The groups were exposed for 60 min twice Grooming did not differ among groups, but yawning diminished with RI. Yawning increased and grooming decreased with the 2nd exposure, except in RI in which grooming increased. In NS and FI grooming prevailed during the first 20 and 30 min, respectively, whereas yawning dominated the remainder of the time. In RI, grooming occurred more than yawning. An upward shift on this scale causes grooming to substitute yawning, whereas a downward shift causes the reverse effect.
The temporal relations among yawning, sleeping, and stretching were investigated by having undergraduate college students record the occurrences of these behaviors during a one-week period. Yawning was most frequent during the hour before sleeping and after waking. In contrast, stretching was common only during the hour after waking. Concurrent yawning and stretching were common but stretching was accompanied more often by yawning than vice-versa. The temporal proximity of yawning to sleep and waking times is probably the basis for yawning as a paralinguistic signal for drowsiness. The role of contagious yawning in synchronizing the behavior and physiological state of a group is considered.
The yawn of the black ape appears to be structurally homologous to the behavior pattern widely described for other vertebrates, even in its finer details. The pattern is highly stereotypic, showing only minor structural variants and not exhibiting any tendency to grade continuously into other expressive or communicative behavior patterns. The yawn occurs in many different contexts, in association with a variety of social and nonsocial situations. Yawns tend to be occur in contexts which elicit some level of stress in the performer. Yawns commonly follw "demonstrations" in which a performer vigorously manipulates an environmental object, with the result of producing a loud noise which draws the attention of others. Adult males yawn significantly more frequently than any other age-sex class. The highest ranking or alpha male tends to yawn at a higher rate than other group members, and in at least one case this was found to be true even following a dominance reversal involving alphas. An ontogenetic trend appears in males: yawning rates increase with age. The most dramatic change occurs during adolescence preceding the eruption of permanent canine dentition. Typical adult male rates are probably reached prior to the completed eruption of the canine teeth.
There have been relatively few empirical or theoretical investigations of the yawning response. Based on field and laboratory research with four vertebrate species, data are presented on yawning frequency. In general, human yawning occurred more frequently in the relative absence of social, cognitive, or physical stimulation; yawning by the other species was more frequent in the presence of such stimulation. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Yawning is a common, species-typical behaviour in vertebrates, generally associated with transitions from sleep to wakefulness. In primates, yawning occurs within a group in a variety of social contexts, suggesting that it has a communicative role, a hypothesis examined in this study. Yawning has rarely been studied. Quantitative studies have been concerned only with age, sex and social-status differences in yawning frequency.
The causation and function of yawning were examined in a quantitative, 796-h ethological analysis of observations of two groups of Cercocebus albigena and one group of Macaca fascicularis. In both species, yawns occurred in two main contexts: during transitions from rest to activity (the ‘rest yawn’) and following social interactions (the ‘emotion yawn’). The rest yawn represents 90 % of yawns and is common to every age-sex group. By contrast, the emotion yawn (10 %) is more frequent in adult males. Regardless of context, yawning was more frequent in males than females. Within males yawning frequency increased with age. Thus, sex hormones may modulate the physiological processes involved. Yawns were usually performed by individuals in seated, lying or standing positions. Yawns were frequently followed by short periods of rest, so that, when triggered by a social interaction, they occurred at its end. The morphology of the yawning act did not vary in regard to context age and/or sex of the yawner.
Interest in personality is growing in a wide range of disciplines, but only in a few systems it is possible to assess the survival value of personality. Field studies looking at the relationship between personality and survival value early in life are greatly hampered by the fact that personality can at present only be assessed after individuals become independent from their parents. In passerines, for example, this is often after a period of intensive selection for the survival on fledglings. The main aim of this study is therefore to develop a method to measure personality before this period of selection. For this purpose, we developed the handling stress (HS) test. We measured HS in 14-d-old great tit nestlings by counting the number of breast movements (breath rate) in four subsequent 15-s bouts for 1 min; before and after they were socially isolated from their siblings for 15 min. To calculate the repeatability of HS, we repeated the test 6 mo later. To assess the relationship between HS and exploratory behaviour, we correlated the outcome of both tests. We ran tests both on birds of lines selected for extreme personality and on wild birds from a natural population. We found that birds selected for fast exploration reacted more to HS compared with birds selected for slow exploration and that HS was repeatable in different life phases. We confirmed this by finding an increase in the HS with increasing exploratory scores in wild birds. These results show that we can use the HS test as a measurement of personality, making it a potential tool for studying the relationship between personality and survival value early in life.
The forms and behavioral correlates of yawning are described, and the phylogenetic and ontogenetic aspects of the act are
examined with particular attention to its possible functions. Much evidence supports the view that yawning is an important
mediator of behavioral arousal levels, a view that is further strengthened by a review of endocrine, neurotransmitter, and
pharmacological mechanisms of yawning: A major function of yawning appears to involve maintenance or increase of arousal when
environments provide relatively little stimulation.
Using human college-age subjects, the present study tested the commonly cited but previously untested hypothesis that yawning is facilitated by higher than normal levels of CO2 or lower than normal levels of O2 in the blood by comparing the effect on yawning of breathing 100% O2 and gas mixtures with higher than normal levels of CO2 (3 or 5%) with compressed air, the control condition. If yawning is a response to heightened blood CO2, the CO2 mixtures should increase yawning rate and/or duration. If low blood O2 produced yawning, breathing 100% O2 should inhibit yawning. The CO2/O2 hypothesis was rejected because breathing neither pure O2 nor gases high in CO2 had a significant effect on yawning although both increased breathing rate. A second study found that exercise sufficient to double breathing rate had no effect on yawning. The two studies suggest that yawning does not serve a primary respiratory function and that yawning and breathing are triggered by different internal states and are controlled by separate mechanisms.
Yawning is a widespread behavioural response expressed in all classes of vertebrates. There is, however, little agreement on its biological significance. One current hypothesis states that yawning serves as a thermoregulatory mechanism that occurs in response to increases in brain and/or body temperature. The brain-cooling hypothesis further stipulates that, as ambient temperature increases and approaches (but does not exceed) body temperature, yawning should increase as a consequence. We tested this hypothesis in a sample of 20 budgerigars, Melopsittacus undulatus, through the manipulation of room temperature. Birds were exposed to three separate conditions (control temperature (22 °C), increasing temperature (22–34 °C), and high temperature (34–38 °C)) in a repeated measures design, with each condition lasting 21 min. The incidence of yawning differed significantly across conditions (4.20 ± 2.39 yawns per bird in the increasing temperature condition, compared to 2.05 ± 1.90 and 1.25 ± 0.72 yawns per bird, in the high temperature and control conditions, respectively). These findings are consistent with the hypothesis that yawning serves a thermoregulatory function.
When mammals, including man, are confronted with a stressful event, their core body temperature rises, stress-induced hyperthermia. In mice, the stress-induced hyperthermia procedure has been developed to measure antistress or anxiolytic-like effects of psychoactive drugs. Group-housed and singly housed versions of the stress-induced hyperthermia generate comparable results. Because the number of animals needed to perform an experiment is much lower in the singly housed versus the group-housed procedure, the former is the test of choice for pharmacological testing. A typical stress-induced hyperthermia test starts with an injection 60 min before the first rectal temperature measurement (T1), followed by a second temperature measurement (T2) 10–15 min later. The difference ΔT (=T2−T1) is the stress-induced hyperthermia. The procedure also measures the intrinsic activity of drugs on the basal body temperature and ΔT is relatively independent from the intrinsic temperature effects of drugs. Anxiolytic drugs (benzodiazepines, -HT1A receptor agonists, alcohol) reduce ΔT suggestive of anxiolytic-like effects. Because the parameter measured for anxiety in the stress-induced hyperthermia procedure is not dependent on locomotor activity, like in almost all other anxiety tests, the stress-induced hyperthermia procedure is an attractive addition to tests in the anxiety field. Because the stress-induced hyperthermia is also present with a comparable pharmacological profile in females, this procedure has a wide species and gender validity. The procedure was applied in various genetically modified mice [5-HT1A and 5-HT1B receptor knockout (KO) mice and corticotropin-releasing hormone overexpressing (CRH-OE) mice] to study phenotypic influences of the various mutations on aspects of anxiety. The stress-induced hyperthermia test in singly housed male and female mice appears a useful and extremely simple test to measure effects of drugs on certain aspects of anxiety or to help to determine phenotypic differences in mutant mice.
Primate yawns are usually categorized according to context (e.g. as a threat, anxious, or rest yawn), but there has been little consideration of whether these yawns are best regarded as a unitary behavior that only differs with respect to the context in which it is observed. This study examined the context and precise morphology of yawns in a group of 11 captive chimpanzees. Focal video sampling was used to describe the morphology and intensity of 124 yawns using ChimpFACS, a system for coding facial movements. Two distinct forms of yawn were identified, a full yawn and a yawn which is modified by additional actions that reduce the mouth aperture. These modified yawns may indicate some degree of voluntary control over facial movement in chimpanzees and, consequently, multiple functions of yawning according to context. To assess context effects, mean activity levels (resting, locomotion, and grooming) and scratching rates were compared one minute before and after each yawn. Locomotion was significantly increased following both types of yawn, whereas scratching rates significantly increased following modified yawns but decreased following full yawns. In terms of individual differences, males did not yawn more than females, although male yawns were of higher intensity, both in the degree of mouth opening and in the amount of associated head movement. These data indicate that yawning is associated with a change in activity levels in chimpanzees, but only modified yawns may be related to increased arousal. Different types of yawn can therefore be differentiated at the morphological level as well as context level.
This report details the case histories of two women who suffer from chronic and debilitating episodes of excessive yawning in the absence of sleep problems.
Each woman independently provided information and answered questions about their excessive yawning symptoms and medical histories.
Both women show signs of thermoregulatory dysfunction, and each reports symptom relief and/or the postponement of yawning attacks through means of behavioral cooling. One woman recorded her body temperature before and after bouts of yawning, revealing a significant drop in temperature following each episode (p < 0.05).
The trigger for yawning in these patients appears to be related to increases in body/brain temperature. These cases are consistent with growing evidence showing that recurrent episodes of excessive yawning are not necessarily associated with a sleep disorder, but rather may be indicative of thermoregulatory dysfunction.
Three eider ducks were handled every 4 min for 16 min to measure their cloacal temperature. This simple handling triggered a rise in their core temperatures from 41.5+/-0.6 degrees C at minute 0 to 43.5+/-0.5 degrees C at minute 16. This increase in body temperature occurred with no obvious motor load from the eiders, but was facilitated by peripheral vasoconstriction and, moreover, was blocked significantly by salicylate, suggesting that the increase in temperature was due to fever. After 10 days of similar handling, the mean fever-like responses displayed by the ducks was significantly lower than their responses of day one, showing a habituation to the emotional stimulation. The eider's heart rate was measured continuously before, during and for a 10-min session following a 1-min handling period. Results showed that the eiders displayed a tachycardia during handling and for 2-3 min posthandling. Such tachycardia is another sign of emotion in animals [Am J Psychol 39 (1927) 106]. Our study showed therefore that eider ducks are prone to emotions and, when emotionally stressed, will display a fever-like response and a tachycardia. Our results on ducks are similar to responses obtained from studies on more terrestrial birds in similar conditions (e.g., chicken [Physiol Behav 69 (2000) 541]), but are in opposition to the bradycardia and the observed decreases in temperature [Hvalradets Skr 22 (1940) 1; Acta Physiol Scand 46 (1959) 231] of birds forcibly submerged.
The authors studied grooming and yawning caused by mild stress in laboratory Sprague-Dawley rats (Rattus norvegicus). Two groups received 3 and 6 sequences of 5 foot shocks at random intervals (RI) and fixed intervals (FI), respectively. A 3rd group was not shocked (NS). The groups were exposed for 60 min twice. Grooming did not differ among groups, but yawning diminished with RI. Yawning increased and grooming decreased with the 2nd exposure, except in RI in which grooming increased. In NS and FI, grooming prevailed during the first 20 and 30 min, respectively, whereas yawning dominated the remainder of the time. In RI, grooming occurred more than yawning. An upward shift on this scale causes grooming to substitute yawning, whereas a downward shift causes the reverse effect.
When mammals, including man, are confronted with a stressful event, their core body temperature rises, stress-induced hyperthermia. In mice, the stress-induced hyperthermia procedure has been developed to measure antistress or anxiolytic-like effects of psychoactive drugs. Group-housed and singly housed versions of the stress-induced hyperthermia generate comparable results. Because the number of animals needed to perform an experiment is much lower in the singly housed versus the group-housed procedure, the former is the test of choice for pharmacological testing. A typical stress-induced hyperthermia test starts with an injection 60 min before the first rectal temperature measurement (T(1)), followed by a second temperature measurement (T(2)) 10-15 min later. The difference DeltaT (=T(2)-T(1)) is the stress-induced hyperthermia. The procedure also measures the intrinsic activity of drugs on the basal body temperature and DeltaT is relatively independent from the intrinsic temperature effects of drugs. Anxiolytic drugs (benzodiazepines, 5-HT(1A) receptor agonists, alcohol) reduce DeltaT suggestive of anxiolytic-like effects. Because the parameter measured for anxiety in the stress-induced hyperthermia procedure is not dependent on locomotor activity, like in almost all other anxiety tests, the stress-induced hyperthermia procedure is an attractive addition to tests in the anxiety field. Because the stress-induced hyperthermia is also present with a comparable pharmacological profile in females, this procedure has a wide species and gender validity. The procedure was applied in various genetically modified mice [5-HT(1A) and 5-HT(1B) receptor knockout (KO) mice and corticotropin-releasing hormone overexpressing (CRH-OE) mice] to study phenotypic influences of the various mutations on aspects of anxiety. The stress-induced hyperthermia test in singly housed male and female mice appears a useful and extremely simple test to measure effects of drugs on certain aspects of anxiety or to help to determine phenotypic differences in mutant mice.
A standard handling protocol was used to test the hypothesis that boldness predicts stress responsiveness in body temperature and breath rate. Great tit (Parus major) nestlings were taken from the field, hand reared until independence, and their response to a novel object was assessed. At the age of 6 months, during the active phase (daytime), body temperature was recorded and breath rate was counted immediately after capture and after 5 min of quiet rest in a bag. A second group of birds of two lines bidirectionally selected for the same trait was tested during the inactive phase (nighttime). During the active phase, body temperature and breath rate were higher in the first than in the second measurement. In the second measurement, shy individuals showed higher body temperature than bold individuals. In the inactive phase, values of both parameters were lower than in the active phase. Body temperature was lower in the first measurement than in the second measurement and no line difference emerged. Breath rate was higher in shy than in bold individuals and did not differ between the two measurements. Females had higher body temperatures than males, probably due to their lower weight, because body temperature was negatively correlated with body mass. The results indicate that body temperature and breath rate are indicators of acute stress in songbirds and that differences in personality traits during the juvenile phase are reflected in differential stress responsiveness later in life.
Although yawning is a ubiquitous and phylogenetically old phenomenon, its origin and purpose remain unclear. The study aimed at testing the widely held hypothesis that yawning is triggered by drowsiness and brings about a reversal or suspension of the process of falling asleep.
Subjects complaining of excessive sleepiness were spontaneously yawning while trying to stay awake in a quiet and darkened room. Changes in their electroencephalogram (EEG) and heart rate variability (HRV) associated with yawning were compared to changes associated with isolated voluntary body movements. Special care was taken to remove eye blink- and movement-artefacts from the recorded signals.
Yawns were preceded and followed by a significantly greater delta activity in EEG than movements (p< or =0.008). After yawning, alpha rhythms were attenuated, decelerated, and shifted towards central brain regions (p< or =0.01), whereas after movements, they were attenuated and accelerated (p<0.02). A significant transient increase of HRV occurred after the onset of yawning and movements, which was followed by a significant slow decrease peaking 17s after onset (p<0.0001). No difference in HRV changes was found between yawns and movements.
Yawning occurred during periods with increased drowsiness and sleep pressure, but was not followed by a measurable increase of the arousal level of the brain. It was neither triggered nor followed by a specific autonomic activation. Our results therefore confirm that yawns occur due to sleepiness, but do not provide evidence for an arousing effect of yawning.
We review a growing body of medical and physiological evidence indicating that yawning may be a thermoregulatory mechanism, providing compensatory cooling when other provisions fail to operate favorably. Conditions such as multiple sclerosis, migraine headaches, epilepsy, stress and anxiety, and schizophrenia have all be linked to thermoregulatory dysfunction and are often associated with instances of atypical yawning. Excessive yawning appears to be symptomatic of conditions that increase brain and/or core temperature, such as central nervous system damage, sleep deprivation and specific serotonin reuptake inhibitors. Yawning is also associated with drowsiness, and subjective ratings of sleepiness are correlated with increases in body temperature. This view of yawning has widespread application for the basic physiological understanding of thermoregulation as well as for the improved diagnosis and treatment of diseases associated with abnormal thermoregulation.
Yawning: no effect of 3e5% CO 2 , 100% O 2 , and exercise Yawning and other maintenance activities in the South African ostrich
- R R Provine
- B C Tate
- L L Geldmacher
- E G F Sauer
- E M Sauer
Provine, R. R., Tate, B. C. & Geldmacher, L. L. 1987b. Yawning: no effect of 3e5% CO 2, 100% O 2, and exercise. Behavioral and Neural Biology, 48, 382e393. Sauer, E. G. F. & Sauer, E. M. 1967. Yawning and other maintenance activities in the South African ostrich. Auk, 84, 571e587.