Fine-grained Variation Research Articles

Can we predict multi-party elections with Google Trends data? Evidence across elections, data windows, and model classes

Google trends (GT), a service aggregating search queries on Google, has been used to predict various outcomes such as as the spread of influenza, automobile sales, unemployment claims, and travel destination planning [1, 2]. Social scientists also used GT to predict elections and referendums across different countries and time periods, sometimes with more, sometimes with less success. We provide unique evidence on the predictive power of GT in the German multi-party systems, forecasting four elections (2009, 2013, 2017, 2021). Thereby, we make several contributions: First, we present one of the first attempts to predict a multi-party election using GT and highlight the specific challenges that originate from this setting. In doing so, we also provide a comprehensive and systematic overview of prior research. Second, we develop a framework that allows for fine-grained variation of the GT data window both in terms of its width and distance to the election. Subsequently, we test the predictive accuracy of several thousand models resulting from those fine-grained specifications. Third, we compare the predictive power of different model classes that are purely GT data based but also incorporate polling data as well as previous elections. Finally, we provide a systematic overview of the challenges one faces in using GT data for predictions part of which have been neglected in prior research.

Heuristic interpretation as rational inference: A computational model of the N400 and P600 in language processing

Much inquiry in psycholinguistics has focused on evidence from the N400 and P600 components of the event-related potential (ERP) signal—and a central theoretical challenge in this area is accounting for the so-called “semantic P600”, which involves unexpected patterns in these components relative to traditional theories of the underlying mechanisms. In this paper we present a computational model of the language processing mechanisms underlying these ERP components, which builds on existing psycholinguistic theories in positing a heuristic interpretation stage of processing, but which deviates from existing theories in formulating this heuristic interpretation process as probabilistic selection via a noisy channel model, and in quantifying and accounting for fine-grained variation in statistical and representational properties of individual stimuli. Our model successfully simulates N400 and P600 patterns from eight psycholinguistic experiments, reflecting the full range of N400-only, P600-only, and biphasic N400-P600 effects, and its behaviors shed light on a number of key patterns that have presented challenges for existing theories. The model’s success indicates that a strong account for the processing mechanisms underlying these effects is one in which language comprehension involves a probabilistic heuristic interpretation stage resembling a noisy channel process, feeding into subsequent processes that assess target word fit and reconcile between heuristic and literal interpretations. The model’s success also indicates that these mechanisms are critically sensitive to statistical variation in individual stimuli, and that modeling the effects of this variation is essential to account for the full range of observed effects in language processing.

A Language-Based Method for Assessing Symbolic Boundary Maintenance between Social Groups

When the social boundaries between groups are breached, the tendency for people to erect and maintain symbolic boundaries intensifies. Drawing on extant perspectives on boundary maintenance, we distinguish between two strategies that people pursue in maintaining symbolic boundaries: boundary retention—entrenching themselves in pre-existing symbolic distinctions—and boundary reformation—innovating new forms of symbolic distinction. Traditional approaches to measuring symbolic boundaries—interviews, participant-observation, and self-reports are ill-suited to detecting fine-grained variation in boundary maintenance. To overcome this limitation, we use the tools of computational linguistics and machine learning to develop a novel approach to measuring symbolic boundaries based on interactional language use between group members before and after they encounter one another. We construct measures of boundary retention and reformation using random forest classifiers that quantify group differences based on pre- and post-contact linguistic styles. We demonstrate this method's utility by applying it to a corpus of email communications from a mid-sized financial services firm that acquired and integrated two smaller firms. We find that: (a) the persistence of symbolic boundaries can be detected for up to 18 months after a merger; (b) acquired employees exhibit more boundary reformation and less boundary retention than their counterparts from the acquiring firm; and (c) individuals engage in more boundary retention, but not reformation, when their local work environment is more densely populated by ingroup members. We discuss implications of these findings for the study of culture in a wide range of intergroup contexts and for computational approaches to measuring culture.

Concepts of variation control systems

Version control systems are an integral part of today’s software engineering. They facilitate the collaborative management of revisions (sequential versions) and variants (concurrent versions) of software systems under development. Typical version control systems maintain revisions of files and variants of whole software systems. Variants are supported via branching or forking mechanisms that conceptually clone whole systems in a coarse-grained way. Unfortunately, such cloning leads to high maintenance efforts. To avoid these disadvantages and support fine-grained variation, developers need to employ custom configuration mechanisms, which leads to a misappropriation of tools and undesired context switches. Addressing this trade-off, a number of variation control systems has been conceived, providing a richer set of capabilities for handling variants. Variation control systems decompose a software system into finer-grained variable entities and offer high-level metaphors to automatically manage this variability. In this paper, we classify and compare variation control systems and illustrate their core concepts and characteristics. All investigated variation control systems offer an iterative (checkout–modify–commit) workflow, but there are essential differences affecting developers. We highlight challenges and discuss research perspectives for developing the next generation of version and variation control systems.

Small spaces, big impacts: contributions of micro-environmental variation to population persistence under climate change.

Individuals within natural populations can experience very different abiotic and biotic conditions across small spatial scales owing to microtopography and other micro-environmental gradients. Ecological and evolutionary studies often ignore the effects of micro-environment on plant population and community dynamics. Here, we explore the extent to which fine-grained variation in abiotic and biotic conditions contributes to within-population variation in trait expression and genetic diversity in natural plant populations. Furthermore, we consider whether benign microhabitats could buffer local populations of some plant species from abiotic stresses imposed by rapid anthropogenic climate change. If microrefugia sustain local populations and communities in the short term, other eco-evolutionary processes, such as gene flow and adaptation, could enhance population stability in the longer term. We caution, however, that local populations may still decline in size as they contract into rare microhabitats and microrefugia. We encourage future research that explicitly examines the role of the micro-environment in maintaining genetic variation within local populations, favouring the evolution of phenotypic plasticity at local scales and enhancing population persistence under global change.

Estimating information cost functions in models of rational inattention

Models of costly information acquisition have grown in popularity in economics. However, little is known about what form information costs take in reality. We show that under mild assumptions on costs, including continuity and convexity, gross payoffs to decision makers are non-decreasing and continuous in potential rewards. We conduct experiments involving simple perceptual tasks with fine-grained variation in the level of potential rewards. Most subjects exhibit monotonicity in performance with respect to potential rewards, and evidence on continuity and convexity of costs is mixed. Moreover, subjects' behavior is consistent with a subset of cost functions commonly assumed in the literature.

Risk assessment based on indirect predation cues: revisiting fine-grained variation.

To adaptively express inducible defenses, prey must gauge risk based on indirect cues of predation. However, the information contained in indirect cues that enable prey to fine-tune their phenotypes to variation in risk is still unclear. In aquatic systems, research has focused on cue concentration as the key variable driving threat-sensitive responses to risk. However, while risk is measured as individuals killed per time, cue concentration may vary with either the number or biomass killed. Alternatively, fine-grained variation in cue, that is, frequency of cue pulses irrespective of concentration, may provide a more reliable signal of risk. Here, we present results from laboratory experiments that examine the relationship between red-eyed treefrog tadpole growth and total cue, cue per pulse, and cue pulse frequency. We also reanalyze an earlier study that examined the effect of fine-grained variation in predator cues on wood frog tadpole growth. Both studies show growth declines with increasing cue pulse frequency, even though individual pulses in high-frequency treatments contained very little cue. This result suggests that counter to earlier conclusions, tadpoles are using fine-grained variation in cue arising from the number of predation events to assess and respond to predation risk, as predicted by consumer-resource theory.

Quantifying how fine-grained environmental heterogeneity and genetic variation affect demography in an annual plant population

The ability of plant species to colonize new habitats and persist in changing environments depends on their ability to respond plastically to environmental variation and on the presence of genetic variation, thus allowing adaptation to new conditions. For invasive species in particular, the relationship between phenotypic trait expression, demography, and the quantitative genetic variation that is available to respond to selection are likely to be important determinants of the successful establishment and persistence of populations. However, the magnitude and sources of individual demographic variation in exotic plant populations remain poorly understood. How important is plasticity versus adaptability in populations of invasive species? Among environmental factors, is temperature, soil nutrients, or competition most influential, and at what scales and life stages do they affect the plants? To investigate these questions we planted seeds of the exotic annual plant Erodium brachycarpum into typical pasture habitat in a spatially nested design. Seeds were drawn from 30 inbred lines to enable quantification of genetic effects. Despite a positive population growth rate, a few plants (0.1 %) produced >50 % of the seeds, suggesting a low effective population size. Emergence and early growth varied by genotype, but as in previous studies on native plants, environmental effects greatly exceeded genetic effects, and survival was unrelated to genotype. Environmental influences shifted from microscale soil compaction and litter depth at emergence through to larger-scale soil nutrient gradients during growth and to competition during later survival and seed production. Temperature had no effect. Most demographic rates were positively correlated, but emergence was negatively correlated with other rates.

Within‐genotype epigenetic variation enables broad niche width in a flower living yeast

Niche theory is one of the central organizing concepts in ecology. Generally, this theory defines a given species niche as all of the factors that effect the persistence of the species as well as the impact of the species in a given location (Hutchinson 1957; Chase 2011). Many studies have argued that phenotypic plasticity enhances niche width because plastic responses allow organisms to express advantageous phenotypes in a broader range of environments (Bradshaw 1965; Van Valen 1965; Sultan 2001). Further, species that exploit habitats with fine-grained variation, or that form metapopulations, are expected to develop broad niche widths through phenotypic plasticity (Sultan & Spencer 2002; Baythavong 2011). Although a long history of laboratory, greenhouse and reciprocal transplant experiments have provided insight into how plasticity contributes to niche width (Pigliucci 2001), recent advances in molecular approaches allow for a mechanistic understanding of plasticity at the molecular level (Nicotra etal. 2010). In particular, variation in epigenetic effects is a potential source of the within-genotype variation that underlies the phenotypic plasticity associated with broad niche widths. Epigenetic mechanisms can alter gene expression and function without altering DNA sequence (Richards 2006) and may be stably transmitted across generations (Jablonka & Raz 2009; Verhoeven etal. 2010). Also, epigenetic mechanisms may be an important component of an individual's response to the environment (Verhoeven etal. 2010). While these ideas are intriguing, few studies have made a clear connection between genome-wide DNA methylation patterns and phenotypic plasticity (e.g. Bossdorf etal. 2010). In this issue of Molecular Ecology, Herrera etal. (2012) present a study that demonstrates epigenetic changes in genome-wide DNA methylation are causally active in a species' ability to exploit resources from a broad range of environments and are particularly important in harsh environments.

Phenotypic plasticity in response to fine‐grained environmental variation in predation

Summary 1 In nature, organisms experience environmental variability at coarse-grained (inter-generational) and fine-grained (intra-generational) scales and a common response to environmental variation is phenotypic plasticity. The emphasis of most empirical work on plasticity has been on examining coarse-grained variation with the goal of understanding the costs and benefits of plastic responses in response to a particular environment. 2 In this study, we investigated the effects of fine-grained variation in predation on the inducible defences of larval wood frogs (Rana sylvatica) by widely altering the density and feeding schedule of caged predators (Dytiscus spp.) while holding average predation constant. 3 We found that predator cues induced change in tadpole behaviour, morphology, and mass. Surprisingly, however, temporal variation in predation did not cause the tadpoles to alter their activity (compared to a constant predation treatment) or mass. Temporal variation in predation did alter tadpole tail depth, but only when experiencing our most extreme variation treatment in which the predators were fed once every 8 days. Under these conditions, the predator-induced tadpole tail was less extreme compared to environments containing constant predation. 4 While a number of previous studies have examined behavioural responses of prey to temporal variation in predation risk without holding average predation constant, this appears to be the first test of temporal variation per se. As in previous studies of organism responses to temporal variation in resources, our results suggest that fine-grained environmental variability can affect the expression of phenotypically plastic traits, but our tadpoles appear to be generally unresponsive to this fine-grained variation for many of their traits.

SATELLITE DETECTION OF BIRD COMMUNITIES IN TROPICAL COUNTRYSIDE

The future of biodiversity hinges partly on realizing the potentially high conservation value of human-dominated countryside. The characteristics of the countryside that promote biodiversity preservation remain poorly understood, however, particularly at the fine scales at which individual farmers tend to make land use decisions. To address this problem, we explored the use of a rapid remote sensing method for estimating bird community composition in tropical countryside, using a two-step process. First, we asked how fine-grained variation in land cover affected community composition. Second, we determined whether the observed changes in community composition correlated with three easily accessible remote sensing metrics (wetness, greenness, and brightness), derived from performing a tasseled-cap transformation on a Landsat Enhanced Thematic Mapper Plus image. As a comparison, we also examined whether the most commonly used remote sensing indicator in ecology, the Normalized Difference Vegetation Index (NDVI), correlated with community composition. We worked within an agricultural landscape in southern Costa Rica, where the land comprised a complex and highly heterogeneous mosaic of remnant native vegetation, pasture, coffee cultivation, and other crops. In this region, we selected 12 study sites (each < 60 ha) that encompassed the range of available land cover possibilities in the countryside. Within each site, we surveyed bird communities within all major land cover types, and we conducted detailed field mapping of land cover. We found that the number of forest-affiliated species increased with forest cover and decreased with residential area across sites. Conversely, the number of agriculture-affiliated species using forest increased with land area devoted to agricultural and residential uses. Interestingly, we found that the wetness and brightness metrics predicted the number of forest- and agriculture-affiliated species within a site as well as did detailed field-generated maps of land cover. In contrast, NDVI and the closely correlated greenness metric did not correlate with land cover or with bird communities. Our study shows the strong potential of the tasseled-cap transformation as a tool for assessing the conservation value of countryside for biodiversity.

Network metrics reveal differences in social organization between two fission–fusion species, Grevy’s zebra and onager

For species in which group membership frequently changes, it has been a challenge to characterize variation in individual interactions and social structure. Quantifying this variation is necessary to test hypotheses about ecological determinants of social patterns and to make predictions about how group dynamics affect the development of cooperative relationships and transmission processes. Network models have recently become popular for analyzing individual contacts within a population context. We use network metrics to compare populations of Grevy's zebra (Equus grevyi) and onagers (Equus hemionus khur). These closely related equids, previously described as having the same social system, inhabit environments differing in the distribution of food, water, and predators. Grevy's zebra and onagers are one example of many sets of coarsely similar fission-fusion species and populations, observed elsewhere in other ungulates, primates, and cetaceans. Our analysis of the population association networks reveals contrasts consistent with their distinctive environments. Grevy's zebra individuals are more selective in their association choices. Grevy's zebra form stable cliques, while onager associations are more fluid. We find evidence that females associate assortatively by reproductive state in Grevy's zebra but not in onagers. The current approach demonstrates the utility of network metrics for identifying fine-grained variation among individuals and populations in association patterns. From our analysis, we can make testable predictions about behavioral mechanisms underlying social structure and its effects on transmission processes.

Coarse‐ versus fine‐grained water stress in Arabidopsis thaliana (Brassicaceae)

The effects of coarse vs. fine-grained variation in water regime on 13 accessions of Arabidopsis thaliana were compared and it was found that the scale of environmental variation can lead to differences in which traits are affected and in the magnitude and direction of effect. Coarse-grained (between individual) variation was studied by comparing plants that received high or low amounts of water on a daily basis. Fine-grained (within individual) variation was distributed across the coarse-grained treatments; plants in the fine-grained treatment received the same amount of water per week as the corresponding high and low coarse-grained treatments; however, in the fine-grained treatments, plants received their entire weekly water allotment over 2 days. The number of leaves produced, days to bolting, length of bolt, number of basal and lateral branches, and survival to 30 days after bolting were measured and analyzed by ANOVA. Plants grown in high water generally produced more leaves, taller main axes, more branches and had increased survival, relative to those in low water. Bolting date showed a significant genotype specific effect of water level. Plants grown under fine-grained variation in watering had taller main axes relative to constant water. There were significant interactions between both types of variation for bolting date, main axis height, and survival. Principal components for all traits were loaded such that the components themselves were also independently affected by genotype, water level, variability of water level (grain), and level-by-grain interactions in ways that were largely predicted by their component traits. Overall, the effects of fine-grained variation were subtler than those of coarse-grained variation: fewer traits responded, and the magnitude of the responses was smaller. Nevertheless, the responses to fine-grained variation are distinct from those of coarse-gained variation, differing with respect to which traits respond and in the direction of response, and must therefore be treated as independent sources of environmental variation.

Selection affecting enzyme polymorphisms in laboratory populations of Drosophila melanogaster.

Gene frequencies at nine polymorphic enzyme loci were followed in 22 cage populations of D. melanogaster all founded from the same stock but subsequently maintained in different environments. The three factors distinguishing the different environments were temperature and the alcohol and yeast in the medium and for each factor each population experienced either a constant or variable condition. The variable conditions were either coarse-grained (period between changes longer than the generation time) or fine-grained (the period less than the generation time).Six polymorphisms were found to be unaffected by any experimental condition. However, the various constant temperatures tested differed in their effects on Alcohol dehydrogenase (Adh), Amylase (Amy) and Isocitrate dehydrogenase (Idh-NADP) gene frequencies. Furthermore, coarse-grained variation between high and low temperatures increased Amy and Idh-NADP heterozygosity and decreased Amy heterozygosity while fine-grained variation between such temperatures promoted Amy heterozygosity. In addition, joint coarse-grained variation for the type of alcohol and yeast promoted Amy and Idh-NADP heterozygosity as well as heterozygosity averaged over all nine loci.In general, the results suggested two major modifications to the hypothesis of a positive relationship between environmental and genetic variability. First, they indicated that the relationship is not always positive. It varies both between loci and between environments. Second however, they indicated that the relationship is more likely to be positive when the environmental variability is coarse- rather than fine-grained.