Professor Zanna Clay's Outputs (47)

Early empathy development: Concern and comforting in 9- and 18-month-old infants from Uganda and the UK (2025)
Journal Article
Vreden, C., Buryn-Weitzel, J. C., Atim, S., Donnellan, E., Hoffman, M., Holden, E., Jurua, M., Knapper, C. V., Lahiff, N. J., Marshall, S., Paricia, J., Tuncgenc, B., Tusiime, F., Wilke, C., Slocombe, K. E., & Clay, Z. (2025). Early empathy development: Concern and comforting in 9- and 18-month-old infants from Uganda and the UK. PLoS ONE, 20(5), Article e0320371. https://doi.org/10.1371/journal.pone.0320371

Empathy, the capacity to share and understand others’ emotional states, is important for navigating our social lives, yet its development in infancy remains poorly understood. Moreover, most research on empathy development has been biased towards Wes... Read More about Early empathy development: Concern and comforting in 9- and 18-month-old infants from Uganda and the UK.

Within-species variation eclipses between-species differences in Pan consolation (2025)
Journal Article
Brooker, J. S., Webb, C. E., Kordon, S., de Waal, F. B., & Clay, Z. (2025). Within-species variation eclipses between-species differences in Pan consolation. Evolution and Human Behavior, 46(3), Article 106682. https://doi.org/10.1016/j.evolhumbehav.2025.106682

Empathy and its subcomponents are well documented throughout the animal kingdom, indicating the deep evolutionary origins of this socioemotional capacity. A key behavioural marker of empathy is consolation, or unsolicited bystander affiliation direct... Read More about Within-species variation eclipses between-species differences in Pan consolation.

Social contagion in primates: Moderating factors and significance for individuals and the group (2025)
Journal Article
Sandars, G., & Clay, Z. (2025). Social contagion in primates: Moderating factors and significance for individuals and the group. Neuroscience & Biobehavioral Reviews, 173, Article 106156. https://doi.org/10.1016/j.neubiorev.2025.106156

Social contagion, which involves behavioural and emotional state matching, is a crucial process for healthy social functioning. In humans as well as other species, it underpins key elements of social interaction, including empathy and social learning... Read More about Social contagion in primates: Moderating factors and significance for individuals and the group.

Bonobos and chimpanzees overlap in sexual behaviour patterns during social tension (2025)
Journal Article
Brooker, J. S., Webb, C. E., van Leeuwen, E. J. C., Kordon, S., de Waal, F. B. M., & Clay, Z. (2025). Bonobos and chimpanzees overlap in sexual behaviour patterns during social tension. Royal Society Open Science, 12(3), Article 242031. https://doi.org/10.1098/rsos.242031

Sexual behaviour during tense social situations is extensively documented in various animals. Bonobos, our closest living relatives alongside chimpanzees, habitually perform genital contacts during social tension, which is thought to enhance cooperat... Read More about Bonobos and chimpanzees overlap in sexual behaviour patterns during social tension.

Conspecific alarm calls, but not food-associated calls, elicit affect-based and object-based mental representations in a bonobo (Pan paniscus) (2025)
Journal Article
Lahiff, N. J., Clay, Z., Epping, A. J., Taglialatela, J. P., Townsend, S. W., & Slocombe, K. E. (2025). Conspecific alarm calls, but not food-associated calls, elicit affect-based and object-based mental representations in a bonobo (Pan paniscus). Royal Society Open Science, 12(3), Article 241901. https://doi.org/10.1098/rsos.241901

Non-human vocalizations carrying information regarding external events have been likened to referential words and are thus integral for exploring the origins of linguistic reference. Previous research suggests receivers decode this referential inform... Read More about Conspecific alarm calls, but not food-associated calls, elicit affect-based and object-based mental representations in a bonobo (Pan paniscus).

Contagious Crying Revisited: A Cross‐Cultural Investigation Into Infant Emotion Contagion Using Infrared Thermal Imaging (2025)
Journal Article
Vreden, C., Renner, E., Ainamani, H. E., Crowther, R., Forward, B., Mazari, S., Tuohy, G., Ndyareeba, E., & Clay, Z. (2025). Contagious Crying Revisited: A Cross‐Cultural Investigation Into Infant Emotion Contagion Using Infrared Thermal Imaging. Developmental Science, 28(2), Article e13608. https://doi.org/10.1111/desc.13608

Contagious crying in infants has been considered an early marker of their sensitivity to others’ emotions, a form of emotional contagion, and an early basis for empathy. However, it remains unclear whether infant distress in response to peer distress... Read More about Contagious Crying Revisited: A Cross‐Cultural Investigation Into Infant Emotion Contagion Using Infrared Thermal Imaging.

Factors shaping socio-emotional trajectories in sanctuary-living bonobos: a longitudinal approach (2024)
Journal Article
Kordon, S., Webb, C. E., Brooker, J. S., de Waal, F. B., & Clay, Z. (2024). Factors shaping socio-emotional trajectories in sanctuary-living bonobos: a longitudinal approach. Royal Society Open Science, 11(12), Article 240435. https://doi.org/10.1098/rsos.240435

Early maternal loss can have lasting detrimental effects on primate social development. While many rehabilitation settings provide enriching environments to buffer against such effects in orphans, previous research indicates that young bonobo (Pan pa... Read More about Factors shaping socio-emotional trajectories in sanctuary-living bonobos: a longitudinal approach.

ChimpanSEE, ChimpanDO: Grooming and play contagion in chimpanzees (2024)
Journal Article
Sandars, G., Brooker, J. S., & Clay, Z. (2024). ChimpanSEE, ChimpanDO: Grooming and play contagion in chimpanzees. PLoS ONE, 19(11), Article e0312467. https://doi.org/10.1371/journal.pone.0312467

Behavioural contagion—the onset of a species-typical behaviour soon after witnessing it in a conspecific—forms the foundation of behavioural synchrony and cohesive group living in social animals. Although past research has mostly focused on negative... Read More about ChimpanSEE, ChimpanDO: Grooming and play contagion in chimpanzees.

Increased alertness and moderate ingroup cohesion in bonobos’ response to outgroup cues (2024)
Journal Article
Brooks, J., van Heijst, K., Epping, A., Lee, S. H., Niksarli, A., Pope, A., Clay, Z., Kret, M. E., Taglialatela, J., & Yamamoto, S. (2024). Increased alertness and moderate ingroup cohesion in bonobos’ response to outgroup cues. PLoS ONE, 19(8), Article e0307975. https://doi.org/10.1371/journal.pone.0307975

In a number of species, including humans, perceived outgroup threat can promote ingroup cohesion. However, the distribution and selection history of this association across species with varied intergroup relations remains unclear. Using a sample of 8... Read More about Increased alertness and moderate ingroup cohesion in bonobos’ response to outgroup cues.

Impact of social context on human facial and gestural emotion expressions (2024)
Journal Article
Heesen, R., Szenteczki, M. A., Kim, Y., Kret, M. E., Atkinson, A. P., Upton, Z., & Clay, Z. (2024). Impact of social context on human facial and gestural emotion expressions. iScience, 27(11), Article 110663. https://doi.org/10.1016/j.isci.2024.110663

Humans flexibly adapt expressions of emotional messages when interacting with others. However, detailed information on how specific parts of the face and hands move in socio-emotional contexts is missing. We identified individual gesture and facial m... Read More about Impact of social context on human facial and gestural emotion expressions.

Frans de Waal - A pioneer who shone a light on the primate mind. (2024)
Journal Article
Clay, Z. (2024). Frans de Waal - A pioneer who shone a light on the primate mind. Neuroscience & Biobehavioral Reviews, 162, Article 105725. https://doi.org/10.1016/j.neubiorev.2024.105725

Biology has just lost one of its greatest thinkers. An intellectual pioneer and exceptional observer of animals, de Waal inspired us all to think differently about animals as well as ourselves - his far-reaching impact within and beyond biology and p... Read More about Frans de Waal - A pioneer who shone a light on the primate mind..

The expression of empathy in human's closest relatives, bonobos and chimpanzees: current and future directions (2024)
Journal Article
Brooker, J. S., Webb, C. E., de Waal, F. B. M., & Clay, Z. (2024). The expression of empathy in human's closest relatives, bonobos and chimpanzees: current and future directions. Biological Reviews, 99(4), 1556-1575. https://doi.org/10.1111/brv.13080

Empathy is a complex, multi‐dimensional capacity that facilitates the sharing and understanding of others' emotions. As our closest living relatives, bonobos (Pan paniscus) and chimpanzees (P. troglodytes) provide an opportunity to explore the origin... Read More about The expression of empathy in human's closest relatives, bonobos and chimpanzees: current and future directions.

Perceptual integration of bodily and facial emotion cues in chimpanzees and humans (2024)
Journal Article
Heesen, R., Kim, Y., Kret, M. E., & Clay, Z. (2024). Perceptual integration of bodily and facial emotion cues in chimpanzees and humans. PNAS Nexus, 3(2), Article pgae012. https://doi.org/10.1093/pnasnexus/pgae012

For highly visual species like primates, facial and bodily emotion expressions play a crucial role in emotion perception. However, most research focuses on facial expressions, while the perception of bodily cues is still poorly understood. Using a no... Read More about Perceptual integration of bodily and facial emotion cues in chimpanzees and humans.

Group-specific expressions of co-feeding tolerance in bonobos and chimpanzees preclude dichotomous species generalizations (2023)
Journal Article
van Leeuwen, E. J., Staes, N., Brooker, J. S., Kordon, S., Nolte, S., Clay, Z., …Stevens, J. M. (2023). Group-specific expressions of co-feeding tolerance in bonobos and chimpanzees preclude dichotomous species generalizations. iScience, 26(12), Article 108528. https://doi.org/10.1016/j.isci.2023.108528

Bonobos are typically portrayed as more socially tolerant than chimpanzees, yet the current evidence supporting such a species-level categorization is equivocal. Here, we used validated group-level co-feeding assays to systematical... Read More about Group-specific expressions of co-feeding tolerance in bonobos and chimpanzees preclude dichotomous species generalizations.

Humans recognize affective cues in primate vocalizations: acoustic and phylogenetic perspectives (2023)
Journal Article
Debracque, C., Slocombe, K. E., Grandjean, D., Clay, Z., & Gruber, T. (2023). Humans recognize affective cues in primate vocalizations: acoustic and phylogenetic perspectives. Scientific Reports, 13(1), Article 10900. https://doi.org/10.1038/s41598-023-37558-3

Humans are adept at extracting affective information from vocalizations of humans and other animals. However, the extent to which human recognition of vocal affective cues of other species is due to cross-taxa similarities in acoustic parameters or t... Read More about Humans recognize affective cues in primate vocalizations: acoustic and phylogenetic perspectives.

Multimodal communication development in semiwild chimpanzees (2023)
Journal Article
Doherty, E., Davila-Ross, M., & Clay, Z. (2023). Multimodal communication development in semiwild chimpanzees. Animal Behaviour, 201(July), 175-190. https://doi.org/10.1016/j.anbehav.2023.03.020

Human language is characterized by the integration of multiple signal modalities, including speech, facial and gestural signals. While language likely has deep evolutionary roots that are shared with some of our closest living relatives, studies of g... Read More about Multimodal communication development in semiwild chimpanzees.

Between-group variation in production of pant-grunt vocalizations by wild bonobos (Pan paniscus) (2023)
Journal Article
Schamberg, I., Clay, Z., Townsend, S. W., & Surbeck, M. (2023). Between-group variation in production of pant-grunt vocalizations by wild bonobos (Pan paniscus). Behavioral Ecology and Sociobiology, 77(1), Article 14. https://doi.org/10.1007/s00265-022-03285-4

The potential for aggression is inherent in social interaction, and strategies to reduce the costs of aggression are ubiquitous among group-living animals. One strategy employed by lower-ranking individuals in a variety of species is the production o... Read More about Between-group variation in production of pant-grunt vocalizations by wild bonobos (Pan paniscus).

The Association Between the Bared-Teeth Display and Social Dominance in Captive Chimpanzees (Pan troglodytes) (2022)
Journal Article
Kim, Y., Vlaeyen, J., Heesen, R., Clay, Z., & Kret, M. (2022). The Association Between the Bared-Teeth Display and Social Dominance in Captive Chimpanzees (Pan troglodytes). Affective Science, 3(4), 749-760. https://doi.org/10.1007/s42761-022-00138-1

Humans use smiles — widely observed emotional expressions — in a variety of social situations, of which the meaning varies depending on social relationship and the context in which it is displayed. The homologue of the human smile in non-human primat... Read More about The Association Between the Bared-Teeth Display and Social Dominance in Captive Chimpanzees (Pan troglodytes).

Flexible signalling strategies by victims mediate post-conflict interactions in bonobos (2022)
Journal Article
Heesen, R., Austry, D., Upton, Z., & Clay, Z. (2022). Flexible signalling strategies by victims mediate post-conflict interactions in bonobos. Philosophical Transactions of the Royal Society B: Biological Sciences, 377(1860), https://doi.org/10.1098/rstb.2021.0310

Compared to other animals, humans supposedly excel at voluntarily controlling and strategically displaying emotional signals. Yet, new data shows that nonhuman great apes' emotion expressions may also be subject to voluntary control. A key context to... Read More about Flexible signalling strategies by victims mediate post-conflict interactions in bonobos.

Bared-teeth displays in bonobos (Pan paniscus): An assessment of the power asymmetry hypothesis (2022)
Journal Article
Vlaeyen, J. M., Heesen, R., Kret, M. E., Clay, Z., Bionda, T., & Kim, Y. (2022). Bared-teeth displays in bonobos (Pan paniscus): An assessment of the power asymmetry hypothesis. American Journal of Primatology, 84(9), Article e23419. https://doi.org/10.1002/ajp.23419

Facial expressions are key to navigating social group life. The Power Asymmetry Hypothesis of Motivational Emancipation predicts that the type of social organization shapes the meaning of communicative displays in relation to an individual's dominanc... Read More about Bared-teeth displays in bonobos (Pan paniscus): An assessment of the power asymmetry hypothesis.