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Fetal yawning assessed by 3D and 4D sonography
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Le bâillement, du réflexe à la pathologie
Le bâillement : de l'éthologie à la médecine clinique
Le bâillement : phylogenèse, éthologie, nosogénie
 Le bâillement : un comportement universel
La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
 
Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal
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mise à jour du
8 mai 2011
Current Zoology
2011;57(4):477-484
No evidence of contagious yawning
in the red-footed tortoise
 
Anna Wilkinson, Natalie Sebanz, Isabella Mand, Ludwig Huber
 
Department of Cognitive Biology, University of Vienna, Austria
Department of Biological Sciences, University of Lincoln, Lincoln, Donders UK
Institute for Brain, Cognition and Behavior, Centre for Cognition, Radboud, University Nijmegen, The Netherlands

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Abstract
Three hypotheses have attempted to explain the phenomenon of contagious yawning. It has been hypothesized that it is a fixed action pattern for which the releasing stimulus is the observation of another yawn, that it is the result of non-conscious mimicry emerging through close links between perception and action or that it is the result of empathy, involving the ability to engage in mental state attribution. This set of experiments sought to distinguish between these hypotheses by examining contagious yawning in a species that is unlikely to show nonconscious mimicry and empathy but does respond to social stimuli: the red-footed tortoise Geochelone carbonaria.
 
A demonstrator tortoise was conditioned to yawn when presented with a red square-shaped stimulus. Observer tortoises were exposed to three conditions: observation of conditioned yawn, non demonstration control, and stimulus only control. We measured the number of yawns for each observer animal in each condition. There was no difference between conditions. Experiment 2 therefore increased the number of conditioned yawns presented. Again, there was no significant difference between conditions. It seemed plausible that the tortoises did not view the conditioned yawn as a real yawn and therefore a fmal experiment was run using video recorded stimuli. The observer tortoises were presented with three conditions: real yawn, conditioned yawns and empty background. Again there was no significant difference between conditions. We therefore conclude that the red-footed tortoise does not yawn in response to observing a conspecific yawn. This suggests that contagious yawning is not the result of a fixed action pattern but may involve more complex social processes
 
tortue pandicule
 
Contagious yawning is well documented in humans, however, little is known about its function and prevalence in the animal kingdom or the brain mechanisms underlying it. The function of yawning itself is also poorly understood. Yawning has been observed in a number of vertebrate taxa and, though it is likely that such a prominent and widespread behaviour serves a biological function, the nature of this function remains unclear (Guggisberg et al., 2007). It has been suggested that yawning may cause an increase in arousal which will reduce the probability of sleep. This is something which is likely to be important for vigilance in all animal species (Walusinski and Deputte, 2004, cited by Guggisberg et al., 2007). Another hypothesis suggests that yawning is a form of communication used to synchronize group behavior (Daquin et al., 2001) this could be for a variety of reasons, those postulated have included communicating drowsiness, social stress or even boredom (Guggisberg et al., 2007). This would potentially serve an important social function and it is possible that contagious yawning may have evolved as a result of this.
 
Experimental analysis of contagious yawning in humans has revealed that it occurs in 40%-60% of participants when they see (videos of) a yawning person (Platek et al., 2005). However, the mechanisms underlying contagious yawning remain poorly understood (Nahab et al., 2009). A number of hypotheses have been proposed to account for the occurrence of contagious yawning and current evidence to support or refute them is equivocal at best. It has been suggested that contagious yawning may simply be the result of a fixed action pattern for which the releaser stimulus is the observation of another yawn (Provine, 1986; Yoon and Tennie, 2010). Evidence to support this hypothesis comes from the fact that yawns follow a highly stereotyped pattern (Provine, 1986). Further, yawning in humans can be triggered by observing a yawn, hearing a yawn (Arnott et al., 2009) or even thinking about yawning (Provine, 1986). This hypothesis predicts that contagious yawning may be observed in all vertebrates that exhibit yawning behavior.
 
A second hypothesis suggests that nonconscious social mimicry, the tendency to adopt postures, gestures and mannerisms of an interaction partner (also known as the chameleon effect; Chartrand and Bargh, 1999) may control contagious yawning behavior (Yoon and Tennie, 2010). Non-conscious mimicry is assumed to reflect close links between perception and action. Many studies in macaque monkeys and humans have shown that when an individual observes another perform a particular action, corresponding action representations in the observer's action repertoire are activated (Rizzolatti and Sinigaglia, 2010). Nonconscious mimicry may occur when inhibitory processes that normally keep us from executing observed actions (Brass et al., 2005) are overridden. It has been shown to be modulated by specific social motivations e.g. the desire to affiliate with the social partner. This is well documented in humans and there is some evidence of this phenomenon in primates (Rizzolatti and Sinigaglia, 2010) but no research has directly examined this in terms of contagious yawning. This hypothesis would predict the presence of contagious yawning in species in which perception and action rely on common neural representations and social relations are of import.
 
The majority of recent research has attempted to explain the phenomenon of contagious yawning in terms of mental state attribution and, in particular, empathy (e.g. Platek et al., 2005). There are many different defmitions of empathy (Vignemont and Singer, 2006), but in this context empathy is considered to be the understanding of another's feelings based on the capacity to infer others' mental states (Baron-Cohen et al., 2005). According to this view contagious yawning should only be observed in those species that possess mental state attribution, and thus we would expect to see little evidence of contagious yawning outside the higher primates.
 
Contagious yawning has been observed in non-human primates (chimpanzees Pan troglodytes, Anderson et al., 2004; stump-tailed macaques Macaca arcto ides, Paukner and Anderson, 2006; gelada baboons Theropithecus gelada, Palagi et al., 2009) and dogs (Canis familiaris, Joly-Mascheroni et al., 2008, but see Han et al., 2009). These studies interpret their data in terms of empathy. However the data presented in these papers do not allow the other hypotheses to be dismissed (see Yoon and Tennie, 2010 for further details) as the studies have focused on those species that may possess the ability to engage in some aspects of mental state attribution or fit the criteria for nononscious mimicry.
 
This study aimed to discriminate between the possible mechanisms controlling contagious yawning by asking whether contagious yawning is present in a species that is unlikely to show empathy or nonconscious mimicry: the redfooted tortoise Geochelone carbonaria. To our knowledge there is no evidence of social mimicry, mental state attribution or empathy in this species. Though naturally solitary there is evidence that this species possesses a sensitivity to visual social cues (Auffenberg, 1965), that it can follow the gaze direction of a conspecific (Wilkinson et al., 2010a) and can learn to access an otherwise inaccessible goal by observing the behavior of a conspecific (Wilkinson et al., 2010b). Further, research suggests that this species is highly visual and when available will use visual cues over both olfactory cues (Wilkinson et al., 2007) and over a highly successful response based behavior (Wilkinson et al., 2009). Taken together this makes them ideal subjects for examining this question. If contagious yawning is simply the result of a fixed action pattern for which the releaser stimulus is the observation of another yawn, then we would expect to observe it in this species; however, if it is controlled through social processes such as nonconscious mimicry or empathy then we would expect it to be absent.
 
 
 
3 Discussion
 
The results of the three experiments presented in this paper suggest that the red-footed tortoise does not yawn in response to observing a conspecific yawn. Experiment 1 examined whether tortoises would yawn more when observing a conspecific perform a conditioned yawn than in other control conditions. They did not. The results revealed that there was no overall difference in responding across conditions suggesting that tortoises do not possess the ability to yawn contagiously. This suggests that contagious yawning may not be the result of a fixed action pattern for which the releaser stimulus is a yawn (Provine, 1986; Yoon and Tennie, 2010) but rather supports the idea that higher level mechanisms such as nonconscious mimicry (Yoon and Tennie 2010) or empathy (Anderson et al., 2004; Paukner and Anderson, 2006; Palagi et al., 2009; Joly-Mascheroni et al., 2008) may control this behavior. However, examination of the individual data revealed an overall low level of responding. Interestingly, of the three animals that did respond two responded more in the yawn condition than in the control conditions. This suggests that the tortoises may have the ability to yawn when they observe a conspecific yawning but it is possible that a single conditioned yawn per trial was not enough to evoke convincing evidence of contagious yawning in this species. The majority of research in this area has used multiple yawns (up to 19, Jolie-Mascheroni et al., 2008) as stimuli. It is therefore plausible that, under experimental conditions, multiple yawns are necessary for contagious yawning to occur.
 
Experiment 2 thus examined whether contagious yawning would be observed if the demonstrator performed multiple conditioned yawns. The results revealed that this was not the case. The tortoises were equally as likely to respond in the control conditions as they were in the experimental conditions. The combined results of Experiment 1 and 2 suggest that the tortoises do not yawn after observing a conspecific yawn. Again, the data contradict the hypothesis that contagious yawning is the result of a fixed action pattern (Provine, 1986; Yoon and Tennie, 2010) and suggests that higher processes such as empathy may be involved (Anderson et al., 2004; Anderson and Matsuzawa, 2006; Paukner and Anderson, 2006; Palagi et al., 2009; Joly-Mascheroni et al., 2008) or nonconscious mimicry (Yoon and Tennie 2010).
 
Experiment 3 examined the possibility that the lack of differential responding observed in the first two experiments was because the conditioned yawn did not appear as a yawn to the tortoises. The results revealed that the animals appeared to respond more in both the yawn and the conditioned yawn conditions than when they were presented with the background control. However, this apparent difference was not close to reaching statistical significance. Thus, the findings of Experiment 3 support those of Experiments 1 and 2 which together reveal that the red-footed tortoise does not yawn in response to observing a conspecific yawn. It is possible that the tortoises did not perceive the video stimuli as a real tortoise and that the experimental stimulus (the conditioned yawn) with which the tortoises were presented may have lacked some elements which, though not apparent to humans, were essential for contagious yawning to take place. For example, the demonstrator was trained to express a simulated yawn by opening its mouth wide and turning its head up. However, a yawn also involves the movement of air and this is something which was not simulated in either our conditioned yawn experiments or in the video playback. It is possible that a real yawn is necessary to stimulate the observer tortoise. Yet, video stimuli have successfully stimulated yawns in a variety of species (Anderson et al., 2004; Paukner and Anderson, 2006) and video stimuli have produced appropriate responses to social stimuli in the red-footed tortoise (Wilkinson et al., unpublished data). However, the use of video stimuli to elicit behavior in animals is controversial because it is not clear what the animals perceive on the screen. This may account for the differences seen between Joly-Macheroni et al.'s (2008) study in which dogs observed a real-life human demonstrator yawning and that of Harr et al. (2009) in which the yawns were presented as video stimuli. Little work has directly investigated pictureobject recognition in reptiles. However, there is evidence that reptiles, including the red-footed tortoise, respond to video stimuli of conspecifics as if they were the real animals (e.g. Ord and Evans, 2002; Ord et al., 2002; Van Dyk and Evans, 2008; Wilkinson et al., unpublished data).
 
Overall, our findings are more consistent with the suggestion that tortoises do not yawn in a contagious manner and that thus suggest that contagious yawning is not simply the result of a fixed action pattern and releaser stimulus, as if this mechanism controlled the behavior it would be predicted that contagious yawning would be present in all vertebrates that yawn. We suggest that contagious yawning may be controlled through social processes such as nonconscious mimicry or empathy, neither of which would have predicted the presence of contagious yawning in the red-footed tortoise. This finding indirectly suggests that, rather than increasing arousal, yawning may be a form of communication that evolved to synchronize group behavior (Daquin et al., 2001). However, the type of information that it might communicate or behavior that it might promote remains unclear. Numerous researchers have suggested that contagious yawning may be an indicator of empathy; however, results in experiments with humans have been equivocal (Platek et al., 2003; Schurmann et al., 2005). The fmdings of this study suggest that contagious yawning may be controlled by higher level social processes as it is believed that tortoises do not possess nonconscious mimicry or empathy. However, the current data do not allow us to determine whether contagious yawning is a result of nonconscious mimicry or empathy. The nonconscious mimicry hypothesis predicts the presence of contagious yawning in species in which perception and action rely on common neural representations we therefore might expect to observe it in animals living in complex social groups. The empathy hypothesis predicts that we would expect to see little evidence of contagious yawning outside the higher primates and (possibly) domesticated dogs, species believed to be capable of empathy (Joly-Mascheroni et al., 2008). Further research is needed to determine which of these social processes may be involved in controlling yawning.