A glimpse of the animal mind: Drivers of affective states in a group-living primate

• Applicant: Dr. Debottam Bhattacharjee, Ph.D.
• Subject Area: Evolution, Anthropology ; Sensory and Behavioural Biology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 563006309

Affective states (or affect), encompassing transient emotions and longer-lasting moods, are psychophysiological inner states that assist us in interacting with changing environments. Impaired regulation of affect can have direct consequences on health and survival, making affective states one of the most widely used indicators of health and well-being. While humans can provide linguistic ‘self-reports’ of their affective states, objective assessment is critical to understanding the inner states of animals. Yet, due to the transient and variable nature of emotions and also moods, their long-term benefits to individuals are often challenging to evaluate. To overcome this, the ‘affective happiness’ framework conceptualises a repetitive summed states approach where relatively stable trait-based benefits of affective states can be evaluated. However, despite recent theoretical advances, the complexity of affect at the intersection of behaviour and physiology hinders the acquisition of empirical data on its mechanisms and implications. Using a group-living primate, the Japanese macaque (Macaca fuscata), this project will employ an interdisciplinary framework to investigate the proximate drivers underlying inter-individual differences in affect and how such variations influence cognitive decision-making processes. The project aims to investigate how socio-ecological (differences in social status and reproductive seasonality) and demographic (ageing) mechanisms drive inter-individual variations in affective states. In addition, the implications of affective states on cognitive performance (inhibition control, memory, and learning) will be tested concurrently. A first-of-its-kind multi-method approach of behaviour (facial expression, vocalisation, kinematics, and sociability and play behaviour), non-invasive physiology (infrared thermography-based nasal temperature, faecal glucocorticoids), and cognition (judgement bias) will be used to measure affective states comprehensively, emphasising affective balance. A standardised cognitive test battery will be used to assess cognitive performance. The project will generate crucial empirical knowledge on these proximate drivers, lay a solid methodological foundation for assessing animal affect to better understand its evolution, and assist in designing informed welfare practices. The major innovative strengths of the project lie in its (a) interdisciplinary framework integrating behaviour, ecology, cognition, and physiology to assess animal affective states, (b) large sample size (n=70) enhancing statistical power, (c) large (4ha) semi-free-ranging environment with natural vegetation, fostering ecological relevance, and (d) completely non-invasive methods with voluntary participation of animals, ensuring their welfare and also setting a precedent for experimental studies in related (semi-) free-ranging animals.

• DFG Programme: Research Grants