Adult human perception of distress in the cries of bonobo, chimpanzee, and human infants

Abstract

19Understanding the extent to which humans perceive the emotional state of animals has both 20 theoretical and practical implications. While recent studies indicate that natural selection has 21 led to some convergence of emotion coding among vertebrate species (including humans), 22highlighting the interspecific value of emotional signals, it has also been argued that 23 interspecific communication of emotions can fail due to species-specific signaling traits 24 impairing information decoding, and/or absence of familiarity with heterospecific 25 communication systems. Here we show that human listeners pay attention to the mean pitch 26 of vocalizations when asked to rate the distress level expressed by human baby cries, and that 27 they use a similar pitch scale to rate the emotional level of baby non-human ape (bonobo and 28 chimpanzee) distress calls. As a consequence the very high-pitched bonobo infant calls were 29 systematically rated as expressing overall high distress levels despite being recorded in 30 contexts eliciting various stress intensity. Conversely, chimpanzee infant calls -which are 31 characterized by a relatively lower-pitch-were systematically rated as expressing relatively 32 lower distress levels. These results indicate that, in the absence of exposure/familiarity, our 33 spontaneous ability to range the emotional content of vocalizations in closely related ape 34 species remains biased by basic frequency differences, suggesting that the absolute 35 interspecific value of emotional signals should not be over-estimated. 36 37 KEYWORDS: acoustic communication -evolutive convergence -ape -bonobo -38 chimpanzee -cry -distress call -emotion -human baby -signal. 39 3

Human temporal voice areas are sensitive to chimpanzee vocalizations

“…This interpretation is strongly supported by the inclusion of acoustic Mahalanobis distance for each species compared to humans as covariate of interest. Additionally, previous research showed a higher pitch in young bonobo screams in comparison to chimpanzee and human baby cries 38 , giving steam to the crucial role of acoustic Mahalanobis distance in our results. Therefore, it seems reasonable to hypothesize that TVA activity is not human-specific 2,6 per se but that it would instead be sensitive to the vocalizations of other primate species, provided that such vocalizations share sufficient acoustic (and phylogenetic) proximity with the human vocal signal.…”

Dog-directed speech: why do we use it and do dogs pay attention to it?

“…Whether this interspecific dimension is innate or acquired through learning remains an open question. It is indeed well established that acoustic signals coding for emotional states share similar acoustic features across mammalian species [33]: although interspecific communication may suffer from limitations [34][35][36], emotion-dependent similarities may derive from shared, ancestral production constraints or reflect convergent evolution in response to common selection pressures [37]. Dogs and wolves emit highpitched tonal vocalizations in greeting contexts, between adults or between cubs, and as a solicitation for food or care [38], and it is likely that puppies are innately receptive to any high-pitched signals with a pronounced harmonicity.…”

Effect of pitch range on dogs’ response to conspecific vs. heterospecific distress cries

“…This suggests that calls are sufficiently close acoustically to be accepted as functionally equivalent and elicit the same behaviour 3 , 24 . However, a study investigating the spontaneous ability of naïve human adults to assess the emotional content of vocalizations in closely related ape species, including bonobos ( Pan paniscus ) and chimpanzees ( P. troglodytes ), showed that listeners responses were strongly biased by basic frequency differences 25 , indicating that in the absence of exposure and/or training, the interspecific relevance of emotional signals can be limited by simple acoustic scaling differences 25 .…”