Human distress vocalizations elicit an increase in dogs' stress responses. This modulation of behaviour to match one's emotional state to that of another individual is often described as emotional ...contagion. Whether this phenomenon is promoted by the dogs' selection for cooperation with humans or is rooted more generally in the universal vocal signals of emotion is unclear. To test this, we compared the reactions of companion dogs, Canis familiaris, and companion pigs, Sus scrofa domesticus (which are popular companion animals but whose domestication history lacks selection for cooperation), to human sound playbacks of crying, a high-arousal, negatively valenced sound, and humming, a low-arousal, less emotionally valenced sound, in a citizen science study. Dogs exhibited higher levels of behaviours associated with increased arousal and negative emotional states and vocalized more in response to crying compared to humming. In contrast, pigs showed more negative and high-arousal behaviours in response to humming than to crying. The fact that dogs seemed to have been affected by and reacted accordingly to the emotional content of human vocal sounds is in line with previous works and the emotional contagion account. In contrast, pigs' elevated stress to the low-arousal humming sound compared to the negative and high-arousal crying sound, cannot be fully explained by emotional contagion but rather by the novelty of the sound (neophobia). Selection for cooperation with humans may thus be key for promoting human sound-induced emotional contagion in domestic mammals.
•We used citizen science data to compare emotional contagion in domestic dogs and pigs.•Dogs showed more stress reactions to a high-arousal, negatively valenced human sound.•Pigs showed higher stress to a low-arousal, less emotionally valenced human sound.•Selection for cooperation may be key for interspecific emotional contagion to emerge.
Family dogs (Canis familiaris) seek human contact from an early age, can discriminate and prefer their caregivers over other humans. To investigate if being kept as a family animal is sufficient to ...induce similar early human proximity-seeking in another domestic mammal, here we directly compared such behaviours in dogs and similarly raised domestic pigs (Sus scrofa domesticus). We used a preference test to measure proximity-seeking behaviours of 4-month-old family pigs and dogs in the presence of their caregiver and either a stranger or a familiar object, in a novel environment. We found that both pigs and dogs preferred their caregivers over the familiar object but not over the stranger. However, when the caregiver and the stranger were present, only dogs showed an overall preference for human proximity, and pigs spent more time away from both humans. These results suggest that both dogs and pigs seek the proximity of their caregiver, but there is a difference in how each species generalizes their experience to other humans. Species-specific predispositions, including that dogs have a longer socialization period and that humans are more salient as a social stimulus for them, may be important for the early development of an overall preference for humans.
During social interactions, acoustic parameters of tetrapods' vocalisations reflect the emotional state of the caller. Higher levels of spectral noise and the occurrence of irregularities (non-linear ...phenomena NLP) might be negative arousal indicators in alarm calls, although less is known about other distress vocalisations. Family dogs experience different levels of stress during separation from their owner and may vocalise extensively. Analysing their whines can provide evidence for the relationship between arousal and NLP. We recorded 167 family dogs' separation behaviour including vocalisations, assessed their stress level based on behaviour and tested how these, their individual features, and owner reported separation-related problems (SRP) relate to their whines' (N = 4086) spectral noise and NLP. Dogs with SRP produced NLP whines more likely. More active dogs and dogs that tried to escape produced noisier whines. Older dogs' whines were more harmonic than younger ones', but they also showed a higher NLP ratio. Our results show that vocal harshness and NLP are associated with arousal in contact calls, and thus might function as stress indicators. The higher occurrence of NLP in older dogs irrespective to separation stress suggests loss in precise neural control of the larynx, and hence can be a potential ageing indicator.
Abstract Dogs exhibit human-analogue attachment to their owners, with similar function and mechanisms to that of infant-mother bond, but its origin is unclear. Comparative studies on socialised ...wolves and dogs emphasise genetic influence in dogs' preparedness for attachment to humans. We aimed to reveal if this genetic effect stems from general domestication or artificial selection that increased dogs' dependence on humans. We assessed and compared behavioural patterns of young companion pigs and dogs using a Strange Situation Test. Dogs but not pigs exhibited distinct behaviours towards their owner and a stranger along attachment-specific variables, so only dogs’ relevant behaviours fulfilled attachment criteria. From the observed behaviours, three factors were formed: Attachment (to the owner), Anxiety (in a strange situation), and Acceptance (of a stranger). Results indicate (1) higher Attachment scores in dogs than pigs, (2) greater Acceptance scores in pigs, (3) positive correlation of Attachment and Anxiety in both, (4) similar time tendency of pigs' Attachment and Acceptance scores. These suggest that in pigs, domestication and early exposure to human social stimuli did not trigger attachment to humans. Thus, along with species predispositions, the unique dog-owner attachment can be facilitated by artificial selection that increased dogs' dependence on humans.
The function of jealous behaviour is to facilitate the maintenance of an important social relationship that is threatened by a third-party, a rival individual. Although jealous behaviour has an ...important function in gregarious species, it has been investigated almost exclusively in humans. Based on functional similarity between dog-owner and mother-infant attachments, we hypothesised that jealous behaviour can be evoked in dogs, similarly to children. In our study owners focused their attention solely on the test partner, while they ignored their dog. We deployed familiar and unfamiliar dogs as social test partners, and familiar and unfamiliar objects as non-social test partners; all subjects encountered all test partners. Dogs showed more jealous behaviour, i.e. owner-oriented behaviour and attempts to separate the owner and test partner in case of social compared to non-social test partners. Results suggest that jealous behaviour emerges in dogs, and it is functionally similar to that in children observed in similar situations. Alternative explanations like territoriality, dominance rank can be excluded.
When facing an unsolvable problem, dogs exhibit spontaneous human-oriented behaviours (e.g. looking at the human partner, gaze alternations between the human and the target) sooner and for longer ...than domestic cats and hand-raised wolves. These behaviours have been interpreted as interspecific communicative acts aimed to initiate interaction. Here, we compare the emergence of human-oriented behaviours (e.g. orientation towards humans, orientation alternations, vocalizations) in similarly raised family dogs and miniature pigs utilising an unsolvable task paradigm which consists of Baseline (no task), Solvable and Unsolvable phases. Relative to the Baseline phase in which both species showed human-oriented behaviours to a similar extent, during the Unsolvable phase dogs showed more and pigs showed less such behaviours. Species-predispositions in communicative behaviour may explain why dogs have a higher inclination than pigs to initiate interspecific interactions with humans in problem-solving contexts.
Human-oriented referential communication has been evidenced not only in domestic but also in some wild species, however, the importance of domestication-unrelated species' characteristics in the ...emergence of this capacity remains largely unexplored. One shared property of all species reported to exhibit referential communication is the efficient use of visual social signals. To assess the potential role of species-specific characteristics in the emergence of human-oriented referential communication, we compared similarly socialised companion animals from two domestic species: dogs, which rely heavily on conspecific visual social signals; and pigs, which do not. We used an out-of-reach reward paradigm with three conditions: both human and reward present, only human present, only reward present. Both species exhibited certain behaviours (e.g. orientation towards the human, orientation alternation between the human and the reward) more often in the human's presence. However, only dogs exhibited those behaviours more often in the simultaneous presence of the human and the reward. These results suggest similar readiness in dogs and pigs to attend to humans but also that pigs, unlike dogs, do not initiate referential communication with humans. The ability to referentially communicate with humans may not emerge in mammals, even if domesticated companion animals, that lack certain species characteristics, such as efficient intraspecific visual communication.
Previous research proves dogs’ outstanding success in socio-communicative interactions with humans; however, little is known about other domestic species’ interspecific skills when kept as companion ...animals. Our aim was to assess highly socialized young miniature pigs’ spontaneous reactions in interactions with humans in direct comparison with that of young family dogs. All subjects experienced similar amount of socialization in human families. In Study 1, we investigated the appearance of human-oriented behaviours without the presence of food (Control condition) when a previously provided food reward was withheld (Food condition). In Study 2, we measured responsiveness to two types of the distal pointing gesture (dynamic sustained and momentary) in a two-way object choice test. In the Control condition of Study 1, the duration of pigs’ and dogs’ orientation towards and their frequency of touching the human’s body was similar. In the Food condition, these behaviours and orienting to the human’s face were intensified in both species. However, pigs exhibited face-orientation to an overall lesser extent and almost exclusively in the Food condition. In Study 2, only dogs relied spontaneously on the distal dynamic-sustained pointing gesture, while all pigs developed side bias. The results suggest that individual familiarization to a human environment enables the spontaneous appearance of similar socio-communicative behaviours in dogs and pigs, however, species predispositions might cause differences in the display of specific signals as well as in the success of spontaneously responding to certain types of the human pointing gestures.
•Separation related problems (SRP) might become more intense with advancing age.•32 dogs were observed during separation from the owner and retested two years later.•41 % of dogs were stable, 38 % ...improved, 16 % worsened in separation behaviour.•Ageing SRP dogs whined more, had higher NLP ratio and made less escape attempts.•SRP dogs should be tested longitudinally to track their individual trajectories.
Separation related problems (SRP) caused by distress associated with separation from the preferred member of the social group, can be characterised by their symptoms e.g., excessive vocalisation. In dogs’ separation whines, nonlinear phenomena (NLP) (abrupt changes in the resonance of the vocal folds) might occur, which could be adaptive in communicating aroused inner states. Previously, using a separation test we found that more dogs that were classified as having SRP by their owner have NLP in their whines than nonaffected dogs and that NLP ratio increases with age, which suggests that separation stress might intensify with age.
We repeated the separation test 21.19 ± 9.37 months later with 32 dogs from the previous study to investigate longitudinally how separation behaviour and vocalisations change with age. Beside behaviour, we measured the acoustic structure of the whines (jitter - small-scale irregularity of the pitch, entropy - vocal harshness, call length, pitch (f0) related parameters, and the spectral components) and calculated the NLP ratio. We formed clusters based on the dogs’ behaviour changes from the first test to the second, to see individual ageing patterns. Finally, we compared the dogs’ behaviour and the acoustic structure of their whines in the two occasions.
We found that dogs could be clustered by the changes in their separation behaviour. 41 % of the dogs were stable over time, 38 % improved, and 16 % showed an increase in their separation behaviours. 3 % switched from barking to whining. Interestingly, SRP dogs were stable, some of them even showed improvement in their separation behaviour. On the contrary, we also found that SRP dogs tended to have an increased NLP ratio with age from test 1 to test 2 (p = 0.09), showed less escape-related behaviour (p = 0.01), but tended to spend more time passively whining at the door through which the owner left the room (p = 0.05), than non-SRP dogs.
The behavioural and vocal results suggest elevated stress levels in SRP dogs with age, although they did not decline but mostly stayed stable in their separation behaviour, confirming that there could be a connection between SRP status, age, and NLP. However, together with the results of the clustering that showed that there are different patterns in dogs’ separation behaviour, we emphasise the importance of individual level longitudinal investigations in order to facilitate the early diagnosis of SRP and to provide a solid basis for the development of individualised treatment plan for SRP dogs.
To evaluate the use of Bowman's layer (BL) vertical topographic thickness maps in diagnosing keratoconus (KC).
Prospective, case control, interventional case series.
A total of 42 eyes: 22 eyes of 15 ...normal subjects and 20 eyes of 15 patients with KC.
Bowman's layer 2-dimensional 9-mm vertical topographic thickness maps were created using custom-made ultra high-resolution optical coherence tomography.
Bowman's layer average and minimum thicknesses of the inferior half of the cornea, Bowman's ectasia index (BEI; defined as BL minimum thickness of the inferior half of the cornea divided by BL average thickness of the superior half of the cornea multiplied by 100), BEI-Max (defined as BL minimum thickness of the inferior half of the cornea divided by BL maximum thickness of the superior half of the cornea multiplied by 100), keratometric astigmatism (Ast-K) of patients with KC, and average keratometric (Avg-K) readings.
In patients with KC, BL vertical thickness maps disclosed localized relative inferior thinning of the BL. Inferior BL average thickness (normal = 15±2, KC = 12±3 μm), inferior BL minimum thickness (normal = 13±2, KC = 7±3 μm), BEI (normal = 91±7, KC = 48±14), and BEI-Max (normal = 75±8; KC = 40±13) all showed highly significant differences in KC compared with normal subjects (P< 0.001). Receiver operating characteristic (ROC) curve analysis showed excellent predictive accuracy for BEI and BEI-Max with 100% sensitivity and specificity (area under the curve AUC of 1) with cutoff values of 80 and 60, respectively. The AUC of inferior BL average thickness and minimum thickness were 0.87 and 0.96 with a sensitivity of 80% and 93%, respectively, and a specificity of 93% and 93%, respectively. Inferior BL average thickness, inferior BL minimum thickness, BEI, and BEI-Max correlated highly to Ast-K (R = -0.72, -0.82, -0.84, and -0.82, respectively; P< 0.001) and to Avg-K (R = -0.62, P< 0.001; R = -0.59, P = 0.001; R = -0.60, P< 0.001; and R = -0.59, P = 0.001, respectively).
Bowman's layer vertical topographic thickness maps of patients with KC disclose characteristic localized relative inferior thinning. Inferior BL average thickness, inferior BL minimum thickness, BEI, and BEI-Max are qualitative and quantitative indices for the diagnosis of KC that accurately correlate with the severity of KC. In our pilot study, BEI and BEI-Max showed excellent accuracy, sensitivity, and specificity in the diagnosis of KC.
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