MAIN RESEARCH INTERESTS
COGNITIVE BASES OF GREAT APE CULTURES
As a PhD student, I designed the first field experiment to be conducted in two wild communities of chimpanzees in Uganda. Field experiments are notoriously hard to conduct in the wild. The ‘honey-trap experiment’ allowed showing that two communities of chimpanzees in two different forests would solve the same problem (honey trapped inside a log) with different tools, in line with their cultural knowledge (Gruber et al. 2009). This study has become a classic in the animal culture literature (over 180 citations so far) and has been replicated in other species (e.g. capuchins) by other researchers. I also replicated this study with wild-born Sumatran orangutans in Indonesia. In this study I also controlled for genetic and environmental difference and found the same results as in chimpanzees (Gruber et al. 2012).
Main papers of interest
Gruber, T.*, Zuberbühler, K., Clément, F. & van Schaik, C.P. (2015) Apes have culture but may not know that they do. Frontiers in Psychology, 6:91. doi: 10.3389/fpsyg.2015.00091
Gruber, T.*, Singleton, I. & van Schaik, C.P. (2012) Sumatran orangutans differ in their cultural knowledge but not in their cognitive abilities. Current Biology, 22(23), 2231-2235. doi: 10.1016/j.cub.2012.09.041
Gruber, T., Muller, M.N., Reynolds, V., Wrangham, R.W. & Zuberbühler, K. (2011) Community-specific evaluation of tool affordances in wild chimpanzees. Scientific Reports, 1, doi: 10.1038/srep00128
Gruber, T., Muller, M.N., Strimling, P., Wrangham, R.W. & Zuberbühler, K. (2009) Wild chimpanzees rely on cultural knowledge to solve an experimental honey acquisition task. Current biology, 19:1806-10. doi: 10.1016/j.cub.2009.08.060
ECOLOGICAL INFLUENCES ON TOOL USE IN THE WILD
Working in the forest in Uganda means having to take into account the daily activity of chimpanzees in the wild to understand why they use tools or not. I thus engaged in the debate on the ecological bases of chimpanzee tool use behavior. Yet, because of my experimental work, I was in the unique position to combine experimental and observational data. In particular, analyzing over eight years of observational and experimental tool use data, we showed that chimpanzees were more likely to use tools when the ecological conditions were the most demanding (Gruber et al. 2016).
Main papers of interest
Grund, C., Neumann, C. Zuberbühler, K. & Gruber, T.* (2019) Necessity creates opportunities for tool use in wild chimpanzees. Behavioral Ecology, 30(4), 1136-1144, doi: 10.1093/beheco/arz062
Gruber, T.*, Zuberbühler, K. & Neumann, C. (2016) Travel fosters tool use in wild chimpanzees. eLife, 5:e16371. doi: 10.7554/ eLife.16371
Gruber, T.*, Potts, K.B., Krupenye, C., Byrne, M.-R., Mackworth-Young, C. McGrew, W.C., Reynolds, V. & Zuberbühler, K. (2012) The influence of ecology on animal cultural behaviour: A case study of five Ugandan chimpanzee communities. Journal of Comparative Psychology, 126(4):446-57. doi: 10.1037/a0028702
Gruber, T.* (2013) Historical hypotheses of chimpanzee tool use behaviour in relation to natural and human-induced changes in an East African rain forest. Revue de Primatologie, 5, document 66. doi: 10.4000/primatologie.1690
SOCIAL LEARNING OF NOVEL BEHAVIOR IN WILD CHIMPANZEES
Together with Cat Hobaiter, we had the opportunity to describe a rare case of social transmission of a novel behavior, moss-sponging, in a wild community of chimpanzees (Hobaiter et al. 2014). This study has become a key paper in the debate on the social transmission of tool use in chimpanzees. Subsequent work by Dr Lamon, then a PhD student at the Univesity of Neuchâtel showed experimentally that moss-sponging continued to spread beyond its initial innovation within family lines, and most likely because it was more efficient than the ancestral behavior, leaf-sponging.
Main papers of interest
Lamon, N., Neumann, C., Zuberbühler, K.§ & Gruber, T.*§ (2018) Wild chimpanzees select tool material based on efficiency and knowledge. Proceedings of the Royal Society B, doi: 10.1098/rspb.2018.1715
Lamon, N., Neumann, C., Gruber, T.§ & Zuberbühler, K.§ (2017) Kin-based cultural transmission of tool use in wild chimpanzees. Science Advances, 3, e1602750. doi: 10.1126/sciadv.1602750
Hobaiter, C., Poisot, T., Zuberbühler, K., Hoppitt, W. & Gruber, T.* (2014) Social network analysis shows direct evidence for social transmission of tool use in wild chimpanzees. PLOS Biology, 12(9): e1001960. doi:10.1371/journal.pbio.1001960
PRIMATE VOCALIZATIONS AND THE ORIGINS OF HUMAN LANGUAGE
During my PhD, I also conducted one of the first studies on intentional vocal behavior in wild chimpanzees (Gruber & Zuberbühler, 2013), stressing that chimpanzee vocalizations are not purely reflections of the emotional states of the individuals producing them. I have continued this work in recent years, investigating cognitive properties (intentionality and reference) in great ape vocalizations (e.g. Sievers & Gruber, 2016 or Crockford, Gruber & Zuberbühler, 2018).
Main papers of interest
Fröhlich, M., Sievers, C., Gruber, T.§, & van Schaik, C. P.§ (2019) Multimodal communication and language origins: integrating gestures and vocalizations. Biological Reviews, doi: 10.1111/brv.12535
Crockford, C. ‡, Gruber, T.*‡ & Zuberbühler, K. (2018) Chimpanzee hoo variants differ according to context. Royal Society Open Science, 5: 172066, doi: 10.1098/rsos.172066
Sievers, C. & Gruber, T. (2016) Reference in humans and non-human primate communication: What does it take to refer? Animal Cognition, 19(4), 759-768. doi: 10.1007/s10071-016-0974-5
Gruber, T.* & Zuberbühler, K. (2013) Vocal recruitment for joint travel in wild chimpanzees. PLOS ONE, 8(9): e76073. doi: 10.1371/journal.pone.0076073
SOCIAL LEARNING IN CHILDREN
I have recently expended my research interests, studying experimentally and cross-culturally phenomena such as conformity and overimitation in children aged three to twelve years old (Gruber et al. 2019; Frick et al. 2017). While there is no denial that humans are the most social species in their learning of tools, the idea here is to put human learning in context and give a fair comparison to other species.
Main papers of interest
Gruber, T.*, Frick, A., Hirata, S., Ikuma, A. & Biro, D. (2019) Spontaneous categorization of tools based on observation in chimpanzees and children. Scientific Reports, 9, 18256, doi:10.1038/s41598-019-54345-1
Gruber, T.*, Deschenaux, A., Frick, A., & Clément, F. (2019) Group membership influences more social identification than social learning or overimitation in children. Child Development. 90(3), 728-745. doi: 10.1111/cdev.12931
Frick, A., Clément, F. § & Gruber, T. § (2017) Evidence for a sex effect during overimitation: Boys copy irrelevant modelled actions more than girls across cultures. Royal Society Open Science, 4, 170367, doi: 10.1098/rsos.170367
AFFECTIVE ASPECTS OF SOCIAL TRANSMISSION AND COMMUNICATION
By joining the Swiss Center for Affective Sciences, I have recently added emotions and neuroscientific methods to my approach to communication and culture. I have developed the use of neuroimaging functional Near-Infrared Spectroscopy for the study of auditive categorization and discrimination (Gruber et al. 2020), which I hope to apply to tool use in the future. We have also developed the use of fNIRS with baboons (Debracque et al. 2021), which opens way to develop non-invasive neuroscience.
Main papers of interest
Gruber, T.*, Bahzydai, M. Sievers, C., Clément, F. & Dukes, D. (2021) The ABC of social learning: Affect, Behaviour and Cognition. Psychological Review, doi: 10.1037/rev0000311
Debracque, C., Gruber, T.*, Grandjean, D.§, & Meguerditchian, A. § (2021) Validating the use of functional Near-Infrared Spectroscopy in monkeys: The case of brain activation lateralization in Papio anubis. Behavioural Brain Research, 403, 113133, doi: 10.1016/j.bbr.2021.113133
Sievers, C. & Gruber, T. (2020) Can nonhuman primate signals be arbitrarily meaningful like human words: An affective approach. Animal Behavior and Cognition, Special Issue Seyfarth, Cheney & Marler 1980, doi: 10.26451/abc.07.02.08.2020
Gruber, T.* , Debracque, C., Ceravolo, L., Igloi, K., Marin Bosch, B., Frühholz, S. & Grandjean, D. (2020) Human discrimination and categorization of emotions in voices: a functional Near-Infrared Spectroscopy (fNIRS) study. Frontiers in Neurosciences, . doi: 10.3389/fnins.2020.00570
Gruber, T.* & Grandjean, D. (2017) A comparative neurological approach to the decoding of vocal emotional expressions in primate vocalisations. Neuroscience and Biobehavioral Reviews, 73, 182-190. doi: 10.1016/j.neubiorev.2016.12.004
