Novel Ground – Charting New Territory
Twin Studies – Ongoing
GERTRUD: Initiating the First German Twin Registry
Baby Lab
1.5 T Mobile MRI
Conclusion
Since its inception, CEN has pioneered the development of a twin registry to better understand the link between the environment and mental health. By enabling genetically controlled studies, CEN can now distinguish between selective migration and direct environmental impacts. To complement this, a new baby lab focuses on early childhood development, while a mobile 1.5T MRI enables the team to study brain function in real-world settings.
Twin Studies – Ongoing
Phenotypes such as human mental health and behavior are shaped by a combination of genetics and environment, including experiences, lifestyle, and living conditions. Since identical twins share almost 100% of their genetic material and fraternal twins about 50%, twin study designs are uniquely placed to help researchers investigate the interplay of genes and environment. CEN has therefore initiated projects with adult and infant twins in order to map the environmental effects on human brain and mental health while controlling for genetic confounding and, in the long run, hopefully gain a better understanding of real-life gene–environment interactions.
GERTRUD: Initiating the First German Twin Registry
Twin studies are vital for disentangling genetic and environmental influences on behavior, health, and the brain. Yet Germany, unlike many other countries in Europe and world-wide, did not have a shared national databank infrastructure. Since 2022, this gap has been closed with the inauguration of GERTRUD (German Twin Registry; www.gertrud.info), a nationwide registry spearheaded by CEN in close cooperation with twin researchers at universities and Max Planck Institutes across Germany. From 2026 to 2031, this effort is being supported by the Strategic Innovation Fund of the Max Planck Society.
GERTRUD is an open registry for mono- and dizygotic twins and higher-order multiples of all ages, designed explicitly to support both classical and extended twin family designs that include parents, siblings, partners, and children. As of late 2025, more than 2,300 individuals have enrolled (including >880 complete twin pairs with an age range of 0–72 years). Over 1,400 have completed a baseline survey covering sociodemographics, mental health, life events, and environmental exposures.
The registry is built as a modular platform with regular core survey waves and embedded add-on studies, ranging from geographic information system (GIS)-based environmental linkage to smartphone-based Geographic Ecological Momentary Assessment (GEMA) protocols, MRI sub-studies, and pilot biobanking. This architecture turns GERTRUD into a common resource for the research community: researchers can contact twins and extended family members via GERTRUD for focused projects while contributing to a growing, interoperable database. In the long run, GERTRUD will be positioned to enable large-scale, multi-source, and longitudinal investigations of gene-environment interplay and prospectively integrate German cohorts into international twin consortia.
GERTRUD Twin Registry
Production: NORDSONNE IDENTITY, Berlin.
Project partners: University Hospital Tübingen, University of Bremen, Bielefeld University, Medical School Hamburg, MPI for Empirical Aesthetics, and Saarland University
Key Reference
The "TwinLife Environment" Study: How Differences in the Environment Relate to Brain Differences in Monozygotic Twins
In the TwinLife Environment study, financed by a Strategic Innovation Fund grant from the Max Planck Society and an ERC-Consolidator grant, CEN aims to capture a wide spectrum of environmental exposures and, at the same time, to separate their associations from genetic and early-life influences. To do so ~310 monozygotic adult twins were recruited and tested, who share (almost) 100% of their genes and a very similar early-life upbringing environment, using structural and functional MRI, intensive environmental assessment, and multi-omics profiling. The researchers characterize the twins' living environments using GEMA: over seven days, the participants carried GPS-enabled smartphones, completed repeated surveys on mood and context, and wore physiological sensors and portable air pollution monitors. These high-resolution data are integrated with GIS-based indicators (e.g., of greenspace, air pollution, noise) and questionnaires. A follow-up wave is currently being collected to examine change–change associations over time.
Ongoing analyses link this multi-level exposome to variation in brain structure, exploiting within-pair differences in exposure. The monozygotic co-twin control design thereby provides a robust way to avoid genetic and early-life confounding. In addition, mediation analyses are being implemented to test whether brain structure mediates associations between environmental exposures and mental health.
NeoTwins: Examining Early Brain Differences in Infant Twin Pairs
The central question of this project is whether monozygotic twins show brain differences shortly after birth, and if so, whether these differences can be linked to specific prenatal environmental influences. Focusing on the prenatal period is particularly relevant, as this vulnerable stage in life is marked by rapid brain development, during which the plastic fetal brain is highly responsive to environmental surroundings. Moreover, the extent of brain differences observable shortly after birth can be understood as a baseline against which differences among twin pairs later in life have to be evaluated.
To accomplish this, the NeoTwins study integrates a comprehensive set of prenatal assessments collected during mid-to-late pregnancy. Interviews, questionnaires, biological samples, GEMA and wearable devices—such as fitness trackers and mobile air-quality sensors—enable detailed measurements of hormonal stress, pollutant exposure, and everyday stressors of the mother. During the first few weeks of life the newborn twins then undergo non-invasive MRI during natural sleep, providing high-resolution measurements of brain structure and function, complemented by biological samples and medical records. The twin design, comprising mono- and dizygotic twins, enables the separation of genetic and environmental contributions. By linking environmental variation to early neural markers, this study will advance understanding of the origins of individual differences in brain development.
Investigating Potential Links Between the Physical Living Environment and Visual Perception in Twins Using Visual Illusions
For a long time, visual perception has been conceptualized as a universal property of the brain, but more recent research has shown that perception is heavily influenced by cultural and environmental factors. Studies with individuals from the Himba tribe, traditional pastoralists living in northwestern Namibia, in a society devoid of modern artefacts, have challenged this assumption, revealing that they exhibit a significantly lower susceptibility to classic visual illusions such as the Ebbinghaus or Müller-Lyer illusion, and can more accurately estimate size ratios. Based on observed differences between rural-dwelling Himba, and Himba who have moved into town-like settlements, it has been hypothesized that the degree of urbanization may have a significant impact on the susceptibility to illusions.
In an ongoing study (N = 274), CEN uses a twin design to account for genetic factors and employs a comprehensive set of tasks involving eight different illusions (Delbeuf, Ebbinghaus, Müller-Lyer, Poggendorff, Ponzo, T-Illusion, Vertical Horizontal, Zöllner) and perceptual style.
By separating the contribution of genetics and the environment, this study will help to explain individual differences in susceptibility to illusions, and may clarify the open question of why the Himba experience almost no illusions. It may also reveal how cognition and perception change when humans move from more rural to urban areas, and potentially why some individuals have more difficulty adapting to city life.
Baby Lab
According to psychoevolutionary concepts such as biophilia theory (Wilson, 1984; Kellert & Wilson, 1995), humans are innately attracted to natural environments, particularly to those that proved to be advantageous in the species' phylogenetic history (e.g., savanna landscapes). Following this line of reasoning, one should plausibly expect a preference for natural landscapes already during infancy. The assumptions of the biophilia theory stand in stark contrast to the more recently proposed conditioned restoration theory, which argues that the preference for and positive effects of nature exposure are acquired through classical conditioning (Egner et al., 2020). CEN sets out to test these early preferences in children and infants; the evidence will provide a basis to decide between these two opposing theories.
Key References
Egner, L. E., Sütterlin, S., & Calogiuri, G. (2020). Proposing a framework for the restorative effects of nature through conditioning: Conditioned restoration theory. International Journal of Environmental Research and Public Health, 17(18), Article 6792. https://doi.org/10.3390/ijerph17186792
Kellert, S. R., & Wilson, E. O. (1995). The biophilia hypothesis. Island Press.
Wilson, E. O. (1984). Biophilia: The human bond with other species. Harvard University Press.
Landscape Preferences in Infancy
How do infants perceive the physical environments that surround them? There is empirical evidence supporting a preference for natural over urban landscapes in adults, while no such effect has been observed in (early) development so far (Meidenbauer et al., 2019). In an ongoing eye tracking study, CEN investigates 7–9-month-old infants' (goal N = 45) visual preferences for natural compared to urban landscapes. Alongside different eye tracking metrics, the researchers collect psychophysiological and parent report measures to explore infants' gaze reactions in relation to arousal levels, previous exposure, and infant temperament. Beyond infants' preferences for natural relative to urban environments, the project has been designed to allow for exploration between different landscape categories and potentially confounding differences in low-level visual characteristics. Once completed, the findings from this project will provide insights into the proposed innateness of specific landscape preferences and contribute to understandings of early brain-environment interactions.
Key Reference
Meidenbauer, K. L., Stenfors, C. U. D., Young, J., Layden, E. A., Schertz, K. E., Kardan, O., Decety, J., & Berman, M. G. (2019). The gradual development of the preference for natural environments. Journal of Environmental Psychology, 65, Article 101328. https://doi.org/10.1016/j.jenvp.2019.101328
Testing the Savanna Hypothesis in Young Children
One specific theory of landscape preference, the "savanna hypothesis," posits that early preference is shaped by human evolution. Studies of landscape preference have concluded that younger children prefer the savanna, whereas adults prefer the landscapes they are more familiar with (Balling & Falk, 1982). However, this conclusion has not been extensively researched or examined in children under the age of 8. Therefore, CEN has developed a paradigm to examine landscape preference in younger children (3–4 years old) by presenting images from six different categories of natural landscapes (savanna, coniferous, deciduous, rainforest, desert, park) and prompting children to rate how much they like what they see. Simultaneously, eye movements are recorded with a screen-based eye tracker (aim N = 45). The goal is to reveal whether children demonstrate a clear preference for the savanna landscape at a young age, as the savanna hypothesis would predict. Through eye tracking, the researchers also hope to investigate differences in visual processing that may underlie landscape preferences.
Key Reference
Balling, J. D., & Falk, J. H. (1982). Development of visual preference for natural environments. Environment and Behavior, 14(1), 5–28. https://doi.org/10.1177/0013916582141001
1.5 T Mobile MRI
In January 2026, CEN welcomed a truck housing a 1.5 T MRI scanner (Figure 2). Previously, studying the effects of walks in the environment required scanning participants in the lab, transporting them to the site of interest, then returning them to the lab for a post-exposure scan. A study utilizing this design by Sudimac et al. (2022) demonstrated that a one-hour walk in Grunewald Forest reduced stress-related amygdala activity, whereas a comparable urban walk on Schloßstraße in Steglitz did not. However, this design limits studies to nearby spaces and prohibits researchers' ability to capture immediate effects.
Mobile MRI enables researchers to scan directly where the exposure happens. Functional MRI data can be acquired directly on site, and comparability issues that come with using multiple scanners can be avoided. CEN aims to study primeval forests (e.g., in Poland) as well as coastal regions and other bluespaces. Mobile MRI also facilitates research with twins and with groups living in extreme conditions, for example, Antarctic overwintering crews (Stahn et al., 2019), and individuals in correctional facilities.
Typically, MRI infrastructure is positioned in hospitals and universities. As these are mostly located in cities, most MRI samples are urban, and rural populations are commonly underrepresented in neuroimaging research, limiting researchers' view on potential differences between rural and urban populations. The mobility offered by the mobile MRI corrects this bias by bringing scanning to rural communities and by lowering participation barriers. CEN plans to run the first study at day-care centers to investigate the neural basis of landscape preferences in young children: families can participate without having to travel, ensuring a more representative sample. Furthermore, CEN is taking first steps toward the on‑site scanning of individuals from the Himba community in Namibia. This unique access will enable researchers to compare human cognition and perception (e.g., color perception, visual illusions, perceptual style) and its underlying brain function and test which findings from predominantly WEIRD (White, Educated, Industrialized, Rich, Democratic) samples replicate in non‑WEIRD, remote populations that most likely compare best to our human ancestors.
Key References
Conclusion
Twin cohorts and the national registry, GERTRUD, provide powerful designs to disentangle environmental from genetic and early‑life influences, enabling within‑pair tests of exposure–brain–behavior links and mediation. Developmental projects (infant and child eye‑tracking and MRI) probe the ontogeny of environmental preferences and test evolutionary versus learned accounts. Mobile 1.5 T MRI brings mechanistic imaging to the exposure site, correcting urban sampling bias, opening access to rural and extreme settings, and enabling immediate post‑exposure scans. Together, these infrastructures expand the funnel's reach: higher control in observational studies (twin/co‑twin control design), better measurement at the right place and time (mobile MRI, GEMA), and higher population validity (non‑WEIRD, lifespan). What is fed back upstream are cleaner effect estimates for long‑term models, stronger short‑term trials, and sharper mechanistic targets for immediate studies.
Taken together, CEN's research program aims to tackle the question of which environmental features have salutogenic or detrimental effects on the brain, well-being, and mental health by examining different time frames of exposure and different levels of inference. This knowledge is essential for urban planning and landscape architecture, since it can inspire and encourage these disciplines to become more empirically grounded. On a societal level, in-depth insights into the specific environmental factors that our brain, well-being, and mental health depend upon will guide much needed predictions of how and on what levels humankind will be impacted by major environmental changes (e.g., caused by climate change or urbanization) and will help to develop mitigation strategies to protect and preserve the human mind.