Natural Experiments Research Articles

Fracking, farmers, and rural electrification in India

The shale gas revolution in the United States induced an unprecedented commodity boom across northwestern India. Leveraging population-based discontinuities in the contemporaneous roll-out of India’s national rural electrification scheme, we show that access to electricity increased total employment and non-agricultural employment in villages affected by this exogenous economic shock, but had no impact on labor markets elsewhere. This combination of two natural experiments highlights how complementary economic conditions drive heterogeneity in the labor-market impacts of rural electrification. It also helps explain the large variation in the reported impacts of such resource-intensive infrastructure investments globally.

Parallel evolution of angiosperm-like venation in Peltaspermales: a reinvestigation of Furcula.

Leaf venation is a pivotal trait in the success of vascular plants. Whereas gymnosperms have single or sparsely branched parallel veins, angiosperms developed a hierarchical structure of veins that form a complex reticulum. Its physiological consequences are considered to have enabled angiosperms to dominate terrestrial ecosystems in the Late Cretaceous and Cenozoic. Although a hierarchical-reticulate venation also occurs in some groups of extinct seed plants, it is unclear whether these are stem relatives of angiosperms or have evolved these traits in parallel. Here, we re-examine the morphology of the enigmatic foliage taxon Furcula, a potential early Mesozoic angiosperm relative, and argue that its hierarchical vein network represents convergent evolution (in the Late Triassic) with flowering plants (which developed in the Early Cretaceous) based on details of vein architecture and the absence of angiosperm-like stomata and guard cells. We suggest that its nearest relatives are Peltaspermales similar to Scytophyllum and Vittaephyllum, the latter being a genus that originated during the Late Triassic (Carnian) and shares a hierarchical vein system with Furcula. We further suggest that the evolution of hierarchical venation systems in the early Permian, the Late Triassic, and the Early Cretaceous represent 'natural experiments' that might help resolve the selective pressures enabling this trait to evolve.

Experimental and numerical study on natural gas explosion evolution in open space under different initial conditions

The vapor cloud explosion in open space are greatly affected by the initial conditions of gas cloud and the surrounding environment, while in the gas compressor station, these factors are ubiquitous. While the researches of external influencing factors like the obstacle and initial turbulence effect on natural gas explosion in open space are rare. In this paper, a series of natural gas explosion experiments were conducted and a long-distance natural gas pipeline compressor station was taking as an example to simulate the natural gas leakage and explosion in the typical location. Results showed that the greater the initial turbulence, the greater the peak overpressure of gas explosion. When the initial wind speed is 5 m/s, the peak overpressure can promote 73.4 % higher than that without initial turbulence. However, the overpressure doesn't linearly increase with the increasing of initial wind speed. What's more, the flame speed showed the same law with the overpressure, and the effect of concentration on overpressure is lower than that of initial turbulence and obstacle density. The explosion damaging range in the condenser area is larger than that in the separator area, and the maximum overpressure can reach about 21 kPa and the temperature can reach above 2280K, which provides an important basis for the safety prevention and personnel protection in natural gas compressor station.

Monitoring Bioindication of Plankton through the Analysis of the Fourier Spectra of the Underwater Digital Holographic Sensor Data.

The study presents a bioindication complex and a technology of the experiment based on a submersible digital holographic camera with advanced monitoring capabilities for the study of plankton and its behavioral characteristics in situ. Additional mechanical and software options expand the capabilities of the digital holographic camera, thus making it possible to adapt the depth of the holographing scene to the parameters of the plankton habitat, perform automatic registration of the "zero" frame and automatic calibration, and carry out natural experiments with plankton photostimulation. The paper considers the results of a long-term digital holographic experiment on the biotesting of the water area in Arctic latitudes. It shows additional possibilities arising during the spectral processing of long time series of plankton parameters obtained during monitoring measurements by a submersible digital holographic camera. In particular, information on the rhythmic components of the ecosystem and behavioral characteristics of plankton, which can be used as a marker of the ecosystem well-being disturbance, is thus obtained.

Improved Method for Determining the Feed Influence on the Tangential Cutting Force During Re-drilling, Countersinking and Boring Based on the Small Sample Theory

Methods of determining the tangential cutting force are analyzed in the work, including finite-element simulation models, the use of neural networks, analytical methods, and methods of natural experiments. A method for evaluating the influence of feed on the tangential component of the cutting force is proposed, which can be applied to test new tools, tool plates for a certain group of materials. The main advantage of the proposed method is the limited number of experiments and processing of the obtained data according to the theory of a small sample. In this study, the proposed method was used to determine the influence of countersinking feed on tangential cutting force. The basis of the approach is probabilistic and statistical methods and data processing criteria. An assessment of the homogeneity of the results of experimental studies was carried out, the law of distribution of the tangential cutting force, as well as the characteristics of its dispersion, were established. An approach to estimating the maximum value of the tangential component of the cutting force based on the maximum value is presented. This method is universal and can be used for drilling, countersinking, boring and other types of processing.

Computational Language Modeling and the Promise of In Silico Experimentation.

Language neuroscience currently relies on two major experimental paradigms: controlled experiments using carefully hand-designed stimuli, and natural stimulus experiments. These approaches have complementary advantages which allow them to address distinct aspects of the neurobiology of language, but each approach also comes with drawbacks. Here we discuss a third paradigm-in silico experimentation using deep learning-based encoding models-that has been enabled by recent advances in cognitive computational neuroscience. This paradigm promises to combine the interpretability of controlled experiments with the generalizability and broad scope of natural stimulus experiments. We show four examples of simulating language neuroscience experiments in silico and then discuss both the advantages and caveats of this approach.

The effect of key universities on the regional development: empirical evidence from two natural experiments in China

ABSTRACT Universities play a crucial role as anchor institutions in regional development. Using the data from the China City Statistical Yearbook from 1995 to 2011, the synthetic control method was employed to examine the impact of key universities on regional development. Results showed that the expansion of higher education significantly influenced the population density in Xuzhou, and per capita output of secondary industry in both Xuzhou and Dongying; yet it has minimal impact on the per capita GDP and average employee wages of the two cities. Thus, key universities may affect regional development by enhancing the quantity and quality of human capital accumulation rather than directly promoting economic growth.

Size matters: Natural experiments suggest the dear enemy effect is moderated by pack size in African wild dogs.

Remote monitoring of communal marking sites, or latrines, provides a unique opportunity to observe undisturbed scent marking behaviour of African wild dogs (Lycaon pictus). We used remote camera trap observations in a natural experiment to test behavioural scent mark responses to rivals (either familiar neighbours or unfamiliar strangers), to determine whether wild dogs exhibit the "dear enemy" or "nasty neighbour" response. Given that larger groups of wild dogs represent a greater threat to smaller groups, including for established residents, we predicted that the overarching categories "dear enemy" vs. "nasty neighbour" may be confounded by varying social statuses that exists between individual dyads interacting. Using the number of overmarks as a metric, results revealed an interaction between sender and receiver group size irrespective of familiarity consistent with this prediction: in general, individuals from large resident packs overmarked large groups more than they overmarked smaller groups, whereas individuals from smaller packs avoided overmarking larger groups, possibly to avoid detection. Monitoring a natural system highlights variables such as pack size that may be either overlooked or controlled during scent presentation experiments, influencing our ability to gain insights into the factors determining territorial responses to rivals.

Call for papers: Generating stronger evidence to inform policy and practice: natural experiments on built environments, health behaviours and chronic diseases

Call for papers: Generating stronger evidence to inform policy and practice: natural experiments on built environments, health behaviours and chronic diseases

Elevation-dependent tree growth response to climate in a natural Scots pine/downy birch forest in northern Sweden.

Forests dominate the landscape at high latitudes in the boreal regions and contribute significantly to the global carbon stock. Large areas are protected and provide possibilities to analyze natural forest dynamics including resilience to climate change. In Fennoscandia, Scots pine (Pinus sylvestris L.) and downy birch (Betula pubescens Ehrh.) often coexist in natural forests close to the limits of their ecological ranges. Tree growth in these forests is generally thought to be limited by temperature, and changes in growth trends can therefore serve as early indicators of the impact of global warming on natural ecosystems. We sampled 592 Scots pine and downy birch trees along two elevational gradients spanning the transition from the forest zone to the coniferous treeline in Tjeggelvas nature reserve, northern Sweden. Based on the tree-ring data, we compared annual basal area increment (BAI) trends from 1902 to 2021, analyzed the ring-width indices (RWI) in relation to local climate data, and investigated trends in climate-growth relationships. We found that the mean annual growth of both species was higher in more recent years than at the beginning of the 20th century. The RWI were positively correlated with summer temperatures, however, we found a much stronger relationship for Scots pine than downy birch. We noticed a decrease in the importance of summer temperature for Scots pine growth, whereas the importance of late spring temperatures increased over the 120-year-long study period. Due to strongly positive BAI trends combined with a decrease in temperature sensitivity, the overall conclusion of our study is that the influence of increasing temperatures is still positive and outweighs the negative impacts of climate change on Scots pine growth in natural forests in northern Sweden, particularly at higher elevations. Natural forests are important natural experiments that contrast the managed forests and are key to understanding the latter.

Quantifying Human Contributions to Near‐Surface Temperature Inversions: Insights From COVID‐19 Natural Experiments

AbstractTemperature inversion (TI) constitutes a crucial component in the physicochemical processes of the lower troposphere, but disentangling human contributions to its generation from complex environmental factors poses significant challenges. We leveraged the unique natural experiment prompted by the coronavirus disease 2019 (COVID‐19) pandemic to estimate changes in TI incidence and temperature difference (∆T) caused by the economic shutdown in the first half of 2020 across 500 major cities worldwide. We found that ∆T declined by 2.5% and TI incidence declined by 18.2% compared to 2016–2019, exhibiting spatial‐temporal heterogeneity and pronounced declines in cities with higher levels of economic development and emission reduction. Moreover, we demonstrated that fine particulate matter (PM2.5) may serve as a mediating pathway through which human activities influence air thermal properties, and climate categories modulate this mediating effect. Our analysis provides empirical evidence of human influence on the vertical thermal structure of the atmosphere.

Abstract P448: Urban Trail Infrastructure and Physical Activity Levels: A Systematic Review and Meta-Analysis of Natural Experiments

Background: In response to climate change, cities across Canada are investing over $1B in new cycling infrastructure to support more active transportation. Little empirical evidence exists describing the effectiveness of adding protected cycling trails on changes in cycling or physical activity (PA) levels. Hypothesis: We hypothesized that areas with new infrastructure would experience increased PA and trail use by cyclists and pedestrians compared to areas without new infrastructure. Design and Methods: We searched CINAHL, EMBASE (Ovid), MEDLINE (Ovid), SPORTDiscus, TRD/Transportation Research Information Services (TRIS), Web of Science and Google Scholar for articles published from 2010 to 2023. We included studies with an experimental pre-post design that reported a PA outcome or trail counts for an intervention and control area. The interventions were limited to protected and/or separated bike lanes, including cycle tracks, multi-use trails, greenways, and bike lanes with concrete barriers. Our primary outcomes were individual level physical activity (PA) and trail use counts (cyclists and pedestrians). A modified risk of bias tool will be employed to assess the methodological quality of each selected study. We followed PRISMA reporting guidelines and the review was pre-registered with Prospero (CRD42023438891) Results: Three independent reviewers screened abstracts from 3936 articles, of which 58 were included in a full text review. After resolving conflicts, 28 articles describing natural experiments of new cycling infrastructure met eligibility criteria were included for data extraction. We extracted data for population characteristics in both intervention and control areas, such as socioeconomic status, mean age, race, and the percentage of females, as well as outcomes related to physical activity. 1/28 papers used accelerometer data, 12/28 used survey data, 3/28 used eco counter data, 2/28 used manual counters. Of the 15 studies that reported it, sample size ranged from 70 to 21,488. Due to high variance in data reporting style, not all studies could be meta-analyzed. We found a high risk of bias for all natural experiments studies and very few adhered to TREND reporting guidelines for quasi-experimental studies. Conclusions: Changes in built environment preliminarily appear to increase cycling and pedestrian counts. Reporting style varies too greatly across research studies for an effective meta-analysis. As a scientific community, we need to work together to follow reporting standards.

Tension between Digital Distance and Physical Presence in Hybrid Teaching: Evidence from Two Natural Experiments During the COVID-19 Pandemic in a French Business School

The advent of digitization has promised learning paradigms based on digital communication and virtual reality at the expense of physical presence. During the COVID-19 health emergency, the tension between digital distance and physical presence evolved from competing alternatives to a more nuanced coexistence. Several organizations resorted to hybrid arrangements; hybrid teaching is a notable example. In this paper, we draw from the theory of planned behavior to theorize the effect of physical presence on learning outcomes in the context of hybrid teaching. We differentiate between individual and team learning outcomes. We predict that physical presence induces competition and has a negative effect on individual learning outcomes. For team learning outcomes, we predict that physical presence induces cooperation and has a positive impact. We exploit two natural experiments in a French business school during the fall semester of 2020. The school’s administration allocated students to subgroups randomly for fairness reasons. This context offered a natural within-subjects experiment, where every student was randomly assigned to either in-person or online lectures. Students had up to 4.9% lower likelihood of correctly answering exam questions for lectures they followed in person rather than online. However, in group-work assignments, teams with one more student following in person tended to see a 3.6% increase in their team evaluation. Digital distance, therefore, constitutes a barrier to learning in a hybrid setting only when tasks are evaluated on a team basis.

Environmental, social, and behavioral challenges of the human circadian clock in real-life conditions.

Urban environments, in which ambient light has become a less-reliable entrainer, are challenging for the biological clock to maintain performance. As a consequence, human circadian rhythms are less robust and more variable among individuals. Assessing the individual phase of entrainment, as well as its plastic shifts in response to disturbances of the physical and social environment, is a way to measure circadian disruption. However, this is still difficult to address in real-life scenarios in which several factors modulate the circadian phase not always in a concerted manner. In this perspective, we present the contribution of two real-life situations, in which the circadian system is challenged by important alterations in entraining signals: 1) a trip to the Antarctic summer (socio-environmental challenge), and 2) dancers trained in morning/night shifts (socio-behavioral challenge). Both natural chronobiological experiments are helpful in exploring the functioning and plasticity of the circadian clock and allow for considering individual characteristics and history.

Solar radio spectrogram segmentation algorithm based on improved fuzzy C-means clustering and adaptive cross filtering

Solar radio spectrograms contain essential information, such as the duration type; therefore, recognizing and detecting solar radio spectrograms are significant for the further study of solar radio. With the upgrading of solar radio observation, considering the equipment that has already generated amounts of data, researchers have begun to use machine learning methods to recognize and detect solar radio spectrograms to resolve the weaknesses of manual identification, such as time consumption. However, the spectrograms are characterized by noise or insignificant outburst features, which affect the recognition and detection of solar radio spectrograms. In contrast, extracting the burst region separately and the more distinctive spectrogram features will help identify and detect it. Therefore, to remove the burst domain of the radio spectrogram better, this paper combines the idea of image segmentation and proposes a solar radio spectrogram segmentation algorithm based on improved fuzzy C-means (FCM) clustering and adaptive cross filtering for the extraction of the burst domain of solar radio spectrograms. This algorithm has multiple processing steps. The first step is solar radio spectrogram segmentation with the improved FCM based on the kernel-induced distance by incorporating spatial constraints combined with random walk and adaptive affiliation linking (RWAKFCM_S). The second step is adaptive cross filtering, eliminating the noise clustered in bursts. The results show the following. (1) The RWAKFCM_S proposed in this paper has better anti-noise and segmentation performance than other methods in the synthetic, natural, and solar radio spectrogram segmentation experiments; it can also overcome the problems of noise sensitivity when segmenting spectrograms by traditional FCM. (2) The RWAKFCM_S can satisfy the high accuracy and rate of solar radio spectrogram segmentation demands. (3) The adaptive cross filtering proposed in this paper can eliminate noise clustered in the eruption domain. (4) The proposed method enables burst region extraction.

Epigenetic aging of human blood cells is influenced by the age of the host body.

Allogenic hematopoietic stem cell transplantation is a therapeutic procedure performed over a wide range of donor and recipient age combinations, representing natural experiments of how the age of the recipient affects aging in transplanted donor cells invivo. We measured DNA methylation and epigenetic aging in donors and recipients and found that biological epigenetic clocks are accelerated in cells transplanted into an older body and decelerated in a younger body. This is the first evidence that the age of the circulating environment influences human epigenetic aging invivo.

Multiple stressors mediate the effects of warming on leaf decomposition in a large regulated river

AbstractPredicting how increasing temperatures interact with other global change drivers to influence the structure and dynamics of Earth's ecosystems is a primary challenge in ecology. Our study made use of multiple simultaneous “natural experiments” to examine how rapid warming, declining nutrients, invasive consumers, and riparian invasive species management interact to influence leaf decomposition in a large and regulated river. Specifically, we compared the breakdown of cottonwood (Populus fremontii), willow (Salix exigua), and saltcedar (Tamarix sp.) leaf litter in 2022 to a previous experiment from 1998 that occurred under much cooler water temperatures, and had higher water phosphorus concentrations, low numbers of invasive New Zealand mudsnails (Potamopyrgus antipodarum), and unaltered litter chemistry from the herbivory of saltcedar leaf beetles (Diorhabda carinulata). We found that the effects of up to 10°C warmer temperatures on leaf decomposition were mediated by the establishment and management of invasive species and declining water nutrient concentrations arising from upstream reservoir lowering. Such interactions led to accelerated breakdown of saltcedar, but relatively minor effects of warming on the rate of cottonwood and willow decomposition. Additionally, our results demonstrate the potential for favorable invasive species management outcomes in the terrestrial environment to produce unintended responses in adjacent freshwater ecosystems. As temperatures continue to rise, it is critical that future studies consider how warming interacts with multiple stressors and environmental factors to influence processes such as decomposition in freshwater ecosystems.

Call for papers: Generating stronger evidence to inform policy and practice: natural experiments on built environments, health behaviours and chronic diseases

Call for papers: Generating stronger evidence to inform policy and practice: natural experiments on built environments, health behaviours and chronic diseases

Intersex in the USA’s Best-Selling Undergraduate Psychology Textbooks: Uneven Critique in an Ongoing Scientific and Ethical Crisis

The field of intersex studies is advancing and requires scholars to update their knowledge and representation of people with intersex variations. To examine how psychology students are taught about people with intersex variations, we reviewed best-selling USA psychology textbooks in introductory psychology (n = 8), psychology of women and gender (n = 5), human sexuality (n = 4), and biological psychology (n = 3). All textbooks indexed intersex or cognate terms, with alternative terms (e.g., disorders of sex development) indexed less frequently. Intersex variations were described as emerging during the stages of sex development, and as challenging binary categories for sex. Several specific variations were commonly described as syndromes with little reference to psychological research or lived experiences. Women and girls with congenital adrenal hyperplasia (CAH) were most clearly framed as “natural experiments” about how nature and nurture intersect. Diverse sex development involving 46 XY genotypes tended to be described as difference from norms for male endosex development. However, two textbooks included lengthy narratives of people’s lived experiences as intersex, and photographs of intersex-identified individuals were common. Photo images of the South African athlete Caster Semenya depicted more of her body than did the photo images of other intersex-identified individuals. The textbooks generally included critical reflection on the assumptions of a gender binary, and on the attribution of ambiguity to others’ bodies, genetic determinism, the medical gaze, and the sex testing of athletes. We consider how information in these textbooks can shape the representation of intersex among psychology students, and how it may be used to develop more humanizing representations of intersex across all psychology textbooks.

Mobile device use and the ranking effect on trading behavior: Evidence from natural experiments

This paper investigates how the trading behavior of investors using mobile devices differs from that of investors using PCs in the context of limited attention. We hypothesize that mobile device-based trading is associated with a stronger “ranking effect” that investors disproportionally trade top-ranked stocks. By exploiting the exogeneity of the return-based ranking of price limit events, we examine the ranking effect on retail investors' buying behavior and find supportive evidence that (1) based on the absolute returns of price limit events, top-ranked stocks are more heavily bought than the lower ranks by investors using mobile devices, while there is no significant ranking effect for investors using PCs; and (2) the ranking effect is enhanced with the increase of the number of contemporaneous price limit events.