Juliette Berthier

PhD student, Biological Anthropology
 Juliette Berthier


PhD project: The role of emotions in the communication of black crested macaques (Macaca nigra). 

Background: Emotions have a central place when studying the proximate mechanisms that underpin animal communication. However, the question of whether emotions have a prevailing or background role in signal production in signallers, and responsiveness in perceivers, still fuels debate and divides animal communication researchers. These divergences of opinions are mainly caused by methodological issues.

For a long time, emotions were thought to be purely subjective and thus not objectively measurable. Consequently, their role in communication and social behaviour in general could only be assumed and not demonstrated empirically. Until recently, scientists lacked reliable and contact-free methods to measure emotions quantitatively and physiologically to perfectly understand their function in signal production and the responsiveness of animals. 

This limitation is now lessened by the improvement in technology during the last decades, including the development of infrared thermo-imaging technology which can be used to assess changes of emotional state by monitoring the activity of the autonomic nervous system objectively and remotely in human and other animals such as non-human primates. Infrared thermography (IRT) could be a valuable tool to test for the intentionality of signal production, and may also allow for a better understanding of the role of emotions in the responsiveness of individuals to signals from others. 

Aims: The aim of this project is to explore the role of emotions in the communication of black crested macaques in their natural environment through the use of IRT in a natural setting. In order to be as exhaustive as possible, several parameters will be taken into account. 

The perspective of both the signaller and the perceiver will be investigated in different contexts (predation, feeding, socio-positive and socio-negative contexts) in order to cover the effects of both the valence (positive vs negative) and the arousal (high, medium and low) of the situations on the emotional state of individuals and their subsequent signal production and responsiveness. The impacts of the audience on the emotional state of callers and subsequent call production will be of particular interest in this project, as well as its effects on the perceivers’ emotional reactivity and their responsiveness. 

Finally, a multimodal approach will be adopted where both vocal (calls) and visual (facial expressions) signals will be studied. The effects of emotions on the production of, and response to, unimodal and bimodal signals will also be investigated. 

The main questions that this project aims to address are: 

  • Are emotions both necessary and sufficient to produce context-specific calls (alarm and food calls)? 
  • Does the emotional reactivity depend on the identity of the caller and drive the responsiveness of perceivers? 
  • Is the different use of unimodal versus multimodal signals under the control of emotions? 
  • What are the impacts of unimodal versus bimodal signals on the internal state of perceivers and on the subsequent behavioural outcomes? 

The methodology that will be used to conduct this project will rely on a combination of playback experiments, presentation of model predator/valuable food items collected in the environment, and behavioural observations coupled with IRT video recording of the faces of the animals. 

Implications: The study of emotions in wild nonhuman animals is a difficult task, but is necessary to test hypotheses about the proximate mechanisms involved in social behaviour generally, and signal production and perception specifically. This research project is expected to provide key new insights not only for our understanding of animal communication, but also of primate sociality and cognition, including the mechanisms involved in behaviours whose ultimate function is explained through kin selection. 

This project may help explain why, from an emotional point of view, individuals are more motivated to invest time and energy in specific, valuable social partners. The use of state-of-the-art technology like the infrared thermography offers a unique and innovative approach to addressing these questions, allowing researchers to use direct, empirical evidence regarding the importance of emotional states in communication and social behaviour, rather than making assumptions about the function of emotions based on intuition and indirect evidence.


Dr Nicholas Newton-Fisher
Dr Brandon Wheeler


Vice-Chancellor's Scholarship, University of Kent

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