Human and space ethology as methodology-based solution for an interdisciplinary research

Carole Tafforin^1*Michel Tognini²

• ¹Independent researcher, Ethospace, France
• ²European Space Agency (ESA), Paris, France

Ethology refers to the term behavioral biology as part of the life sciences. When it comes to human in space, this discipline represents the full scope and evolution of a specific methodology whose feasibility has been demonstrated in field research. The very first example was the effect of microgravity on the astronaut's motor behavior during short-term missions. We have compiled a repertoire of movements, postures, orientations and positions developed objectively for the observation, description and quantification of behavioral manifestations. These are the three specific tools used to investigate the relationship between the individual and his/her environment. Current examples include the effect of confinement and isolation on the social behavior during extended periods of time simulating missions to the Moon and Mars (Tafforin, 2022). The behavioral repertoire has been expanded to actions, interactions, expressions and communications. It allows research and study of global human adaptation to a wide range of environments and analogs such as parabolic flights, space shuttles, orbital stations, Arctic expeditions, Antarctic bases and confinement campaigns (Tafforin et al., 2023). The results showed that human and space ethology is at the interfaces of a panel of disciplines with a common topic of how the organism's components work together to maintain a healthy state.The Nobel prize in medicine or physiology was awarded to Ivan Petrovitch Pavlov for his work on conditioned reflexes (Pavlov, 1927). These were seminal examples of how to study the connections between a behavioral action (e.g. eating), a sensory signal (e.g. bell ringing) and a biological response (e.g. salivation). This emphasized interdisciplinary nodes, such as connections between physiology (metabolic parameters) and behavior (motor actions). Major human mechanisms, be they physiological, behavioral or cognitive, should be studied using methods and tools specific to each discipline. The goals are a systemic approach and a holistic analysis of exhaustive research data.Figure 1 illustrates the different components as wheels with sub-mechanisms and inter-connections. (1) The physiological <-> behavioral connection is related to the endocrinal, neural, metabolic, vestibular, muscular primitive functions that underlie the behavioral emergence in terms of motor skill and motor performance. The ethological observations can be made at the physiological time scale, since the level of precision is less than one second in the encoding of state and point events from video recordings.(2) The behavioral <-> cognitive connection is related to body schema, group image resulting from cognitive mechanisms that work with behavioral activities such as actions at the individual scale and interactions ate the social scale. The ethological observations through quantitative descriptions of the items from the astronaut's repertoire can account for cultural cohesion, emotional workload in daily life activities, scientific and operational activities in international space mission.(3) The physiological <-> cognitive connection is related, with advanced technologies and new medical developments, to correlations of data collected from both cerebral activities, cognitive tasks, and the whole battery of psychological tests. The ethological observations can help in the quantitative description of behavioral indicators (e.g. collateral actions, facial expressions, body orientations and postural changes) that predict etiological factors as assumed in space medicine. The goal is to corroborate physical health, mental health and behavioral health.Are the measuring tools effective for all these interfaces? Each discipline has assessment methods and measurement devices but they do not take into account the human being in its interconnected mechanisms for measuring integrative functions. In space, at the cardio-vascular level, the lack of gravitational force induces a blood shift that generates increased cardiac output and venous flow, stimulates endocrine receptors, and returns metabolic regulation to its original state. At the same time at the sensorimotor level, microgravity induces modifications in the inputs of visual receptors, proprioceptive receptors, musculo-articular receptors and cutaneous receptors. Cognitive responses and behavioral strategies are also being built. It requires a methodology-based solution for such interplanetary research.The components and mechanisms involved in human adaptation within the framework of space life sciences are the outcomes of a systemic approach. An ethological monitoring of the astronaut's behavioral activities allows for highlighting links between systems in an integrated model. Such a systemic approach showed connections between a hard-system which functions just like conservative regulations in the physiological sphere to restore the homeostasis, and a soft-system which functions just like innovative regulations in the motor behavior sphere to create new strategies (Custaud et al., 2020). At the upper cognitive sphere, an informative-system would be used just like initial or final integrations that provide dynamic outputs about the links between the other two. A longitudinal and observational method is an appropriate solution in the search of multi-modal changes over time during long-term exploration missions.A comprehensive example is in confinement, under Mars-like conditions, including a closed-loop system, namely Controlled Ecological Life Support System (CELSS) (Yuan et al., 2019). The multisystem adaptation study was unique in its design over a 180-day experiment. On one hand, body composition, cardiovascular state, metabolic state, endothelial state and muscle state were investigated using biological functional and morphological measurements. On the other hand, recovery-stress state and positive or negative mood were assessed through psychological questionnaires. At the interfaces, behavioral activity through ethological observations revealed interrelationship between the systems evidenced for a particular subject. Results showed the greatest collateral acts-to-facial expressions suggesting a shift in the balance between stressful conditions and well-being state toward stress, along with the lowest cardio-vascular fitness and the highest losses in lean mass and body water.An integrative example is also during a 370-day confinement experiment of crews in the high-closure mission called "Lunar Palace 365" (Fu et al., 2025). It supported for advanced innovations in biomedical engineering, environmental biology and life support technology (e.g., optimizing closure reaches 98.2% of materials being recycled and regenerated for human long-term survival in lunarlike environment). From individual survivability, upon biological needs, to social adaptability, upon behavioral requirements, a systemic approach is relevant.Currently, challenging missions aboard the International Space Station (ISS) reach a year-long exposure to microgravity, cosmic radiations, confinement, isolation and other less studied epigenetic factors. The Space Twins study (Garrett-Bakelman et al. ( 2019) offered this opportunity. The multiomic, molecular, physiological and behavioral data sets provided a valuable roadmap for future studies. Changes described in this multidimensional analysis serve as a guide for targeted countermeasures and monitoring during future crewed missions.From the perspective of deep space exploration, the idea would be to progress from multidisciplinary contributions (Blackwell Landon et al., 2018) to interdisciplinary research with holistic analysis (i.e., treating the human being as a whole in its physical, mental, social, cultural and environmental aspects within an ecosystem) with exhaustive and multimodal data. A final goal would be outputs such as behavioral health and well-being of the space explorers for the success of their missions. Fundamental issues of adaptation and countermeasures have been reported and research gaps have been identified (Pagnini et al., 2023). Questions are for instance: What variables capture relevant information on behavior and performance? What physiological biomarkers provide valid insight into the psychological experience of the astronauts? What methods, measures and metrics should be used to monitor crewmembers and crew functions?Solutions could be international standard measures such as those conducted during the Artificial Gravity Bed Rest with European Space Agency (AGBRESA) study (Clément et al., 2022). Simultaneous video recordings for ethological encoding, as recurrent protocols, could enrich space databases for the scientific community. In addition, collaborative system usability of audio recordings by tracking conversations may serve to assess workload in remote environments (Shelat et al., 2024). Similarly, the combination of cardiovascular measures and speech signals, as demonstrated in the aeronautic environment (Magnusdottir et al., 2022), would complement a holistic analysis.In the space domain, there are devices applied at the personal scale such as the Facial Action Coding System (FACS) for collecting data on crewmembers emotion (Ekman and Friesen, 1978), and at the interpersonal scale such as the Wireless Group Structure (WLGS) module for collecting data on crew cohesion (Johannes et al., 2015) or sociomapping (Sykorova et al, 2024). Innovative applications could be a non-invasive "all-in-one" and "all-at-once" tool to collect behavioral data in the category of expressions (vs. face reader), the category of interactions (vs. sociometer), the category of movements-postures-orientations (vs. actimeter), the category of positions (vs. geolocalized tracking) and the category of communications (vs. audiometer) (Figure 2). Such human and space ethology as methodology-based solution would contribute to the concept of an Ethometer. In control room of a manned space mission, one could imagine joint areas of teleoperation (e.g. ultrasound images) (Greaves, 2019) and ethometric information (e.g. rate of behavioral occurrences) in live video observations or offline video observations. This could lead to innovations in the validation of new countermeasures and support for astronauts on deep space missions. Virtual reality technologies, voice assistants and digital companions are the prospects (Gushin et al., 2021). Validation and corroboration of real behaviors and virtual behaviors are the resulting prospects (Tafforin, 2024). Comparisons could be made with digital twins. Human factors are also concerned in the detection of preventable human errors for the mission success (Pasquier et al., 2019). A particular focus is on well-being and life-support on the Moon and beyond (Tafforin and Tamponnet, 2025). Methodological applications with respect to the interdisciplinary research of countermeasures such as greenhouses in the future space habitats, will help in creating an Earth-like micro-environment that supports a micro-society functioning in social self-organization and vital self-resources.In order to promote further advances in space, as well as applications on Earth, research needs continued sharpening in several areas. An example would be on astronauts' body orientation multianalyses to find out the disorientation processes involved in Alzheimer's disease. Corroborated Magnetic Resonance Images (MRIs) and cognitive tasks in the cerebral plasticity (Romand-Meunier, 2019) via the ethological approach would be a useful methodology-based solution to better understand behavioral adaptation. Scientific openings are optimistic opinions aimed at expanding the frontiers between academic activities and logistic developments, thus leading to novel cooperative programs. A realistic opinion is to remain attentive to maintain the bases of life sciences in the heart of concrete space research program. Human mechanisms are complex and the human observer has an irreplaceable potential as usage innovation to understand them.Astronautic recommendations are to consider soft skills as essential for manned missions because living and working in confined spaces, under pressure and in weightlessness require much more than technical skills. Space agencies are looking for candidates with exceptional interpersonal and psychological abilities. We do not forget task skills but we do add soft skills according to several aspects defined in the Human Behavior and Performance (HBP) competencies model (NASA, 2008). Challenges for exploration missions will require combined tools and methods in the assessment of all these behavioral markers and the biomarkers. Social sciences and life sciences are coming together for the future of humans in space.