Cross-species discrimination of vocal expression of emotional valence by Equidae and Suidae

Abstract

Background Discrimination and perception of emotion expression regulate interactions between conspecifics and can lead to emotional contagion (state matching between producer and receiver) or to more complex forms of empathy (e.g., sympathetic concern). Empathy processes are enhanced by familiarity and physical similarity between partners. Since heterospecifics can also be familiar with each other to some extent, discrimination/perception of emotions and, as a result, emotional contagion could also occur between species. Results Here, we investigated if four species belonging to two ungulate Families, Equidae (domestic and Przewalski’s horses) and Suidae (pigs and wild boars), can discriminate between vocalizations of opposite emotional valence (positive or negative), produced not only by conspecifics, but also closely related heterospecifics and humans. To this aim, we played back to individuals of these four species, which were all habituated to humans, vocalizations from a unique set of recordings for which the valence associated with vocal production was known. We found that domestic and Przewalski’s horses, as well as pigs, but not wild boars, reacted more strongly when the first vocalization played was negative compared to positive, regardless of the species broadcasted. Conclusions Domestic horses, Przewalski’s horses and pigs thus seem to discriminate between positive and negative vocalizations produced not only by conspecifics, but also by heterospecifics, including humans. In addition, we found an absence of difference between the strength of reaction of the four species to the calls of conspecifics and closely related heterospecifics, which could be related to similarities in the general structure of their vocalization. Overall, our results suggest that phylogeny and domestication have played a role in cross-species discrimination/perception of emotions.

Humans read emotional arousal in monkey vocalizations: evidence for evolutionary continuities in communication

“…An additional issue is whether heterospecific emotion perception is best explained by evolutionary homology, familiarity, or domestication ( Maigrot, Hillmann & Briefer, 2022 ). Most previous studies of human perception have used sounds from domestic animals such as cats, dogs, and livestock (for exceptions, see Filippi et al (2017a) , Kelly et al (2017) , Fritz et al (2018) and Kamiloǧlu et al (2020) ).…”

“…These, of course, are species with which many humans are familiar—and indeed, which might have undergone evolutionary changes in emotional expression to improve communication with humans ( Pongrácz, Molnár & Miklósi, 2010 ). Some studies have suggested accurate perception does not depend on familiarity ( Pongrácz et al, 2005 ; Filippi et al, 2017a ; Merkies, Crouchman & Belliveau, 2021 ; Maigrot, Hillmann & Briefer, 2022 ), but several have demonstrated an association between experience with a particular species and increased accuracy in recognizing the emotional significance of its vocalizations ( Nicastro & Owren, 2003 ; McComb et al, 2009 ; Tallet et al, 2010 ; Scheumann et al, 2014 ; Faragó et al, 2017 ; Parsons et al, 2019 ). This raises the question of the degree to which human accuracy in heterospecific emotion recognition tasks reflects evolutionary homology, as opposed to a capacity to learn to recognize any individual species’ unique emotional expressions through exposure.…”

Goat Discrimination of Emotional Valence in the Human Voice

“…Through multiple generations of this interdependent relationship, goats and other domesticated species have undoubtedly become well-adapted to occupying this anthropogenic niche, perhaps predisposing them towards more advanced social cognition of our cues (Hare et al, 2005), including emotional ones. This appears to be the case in pigs, with domestic pigs but not wild boar (Sus scrofa) behaving differently to human voices based on the valence they express (Maigrot et al, 2022).…”

“…Despite this, some livestock have been shown to read a variety of human cues sometimes showing comparable levels of performance to companion animals. For example, pigs (Sus scrofa domesticus) respond differently to human voices based on their emotional valence (Maigrot et al, 2022) and cows (Bos taurus) can discriminate chemical cues, preferring to interact with sweat odours collected from humans in neutral, but not in stressful situations (Destrez et al, 2021).…”

Effects of domestication on responses of chickens and red junglefowl to conspecific calls: A pilot study

“…However, research on whether domestic animals interpret distress and alarm calls as such and react to them accordingly is still limited and may present some contradictions. For example, previous work on pigs revealed that individuals showed similar behavioral and physiological reactions following the playbacks of both conspecific distress calls and a neutral control sound [30], while recent research revealed a contrary pattern: pigs do discriminate negative and positive conspecific vocalizations (vocalizations made during social isolation and when in pairs, with access to food, water, and toys, respectively) [32].…”