Bounding the Inefficiency of Compromise in Opinion Formation

Social networks on the Internet have seen an enormous growth recently and play a crucial role in different aspects of today’s life. They have facilitated information dissemination in ways that have been beneficial for their users but they are often used strategically in order to spread information that only serves the objectives of particular users. These properties have inspired a revision of classical opinion formation models from sociology using game-theoretic notions and tools. We follow the same modeling approach, focusing on scenarios where the opinion expressed by each user is a compromise between her internal belief and the opinions of a small number of neighbors among her social acquaintances. We formulate simple games that capture this behavior and quantify the inefficiency of equilibria using the well-known notion of the price of anarchy. Our results indicate that compromise comes at a cost that strongly depends on the neighborhood size.

The Effects of Orthographic Neighborhood Size and the Influence of Individual Differences in Linguistic Skills During the Recognition of Chinese Words

There are still inconsistencies as to whether frequency and orthographic neighborhood size affect the reading and recognition of Chinese words. In addition, research on Chinese reading still adheres to the view that “all skilled readers read in the same way” and pays little attention to the influence of individual differences in linguistic skills on word recognition. In this research, we studied the recognition of Chinese two-character words in a lexical decision task (LDT) by manipulating neighborhood size and word frequency and controlling the frequency of the initial constituent character. Individual differences in linguistic skills were assessed through tests of spelling and reading comprehension. The results showed that: (1) A larger orthographic neighborhood size of the initial character had a facilitative effect on Chinese word recognition. The orthographic neighborhood size effect is modulated by word frequency, but this modulation effect was not stable. (2) Spelling and reading comprehension skills are good indicators to assess individual differences in Chinese linguistic skills, and they are significantly correlated. (3) Individual differences in linguistic skills influence the neighborhood size effect, which is moderated by word frequency.

When Does Mutualism Offer a Competitive Advantage? A Game-Theoretic Analysis of Host-Host Competition in Mutualism

Questions: Can resource-resource trade mutualism offer a competitive advantage to plants? If so, what are the conditions that give mutualism an advantage especially with regard to the size of the neighborhood? Hypothesis: We hypothesized that mutualism could offer a competitive advantage if the benefits outweighed the costs. We also hypothesized that this competitive advantage could lead to coexistence between mutualist and non-mutualist strategies within the same population. We also hypothesize that local neighborhood size (the number of competitors at a given moment) would change this response, though the specific direction of change was unclear to us. Method: We created an evolutionary game theoretic model in which a plant could either be a mutualist or non-mutualist that incorporated nutrients freely available to the plant, nutrients obtained only through mutualism with microbes, the cost of producing roots, the cost of trade with microbes, and neighborhood size. We sought ESS solutions as defined by the Nash equilibrium criterion. Key Assumptions: 1) Costs and benefits are fixed for all plants. 2) Freely available nutrients are equally shared between all competing plants in a local neighborhood. 3) Microbially obtained nutrients are shared equally between mutualistic plants in the local neighborhood. Conclusion: We found that mutualism could offer a competitive advantage if the net benefit was positive. Coexistence between mutualist strategies in our model happens because of competition between mutualists over the microbially available nutrient. Coexistence was more likely with greater neighborhood size but at the expense of mutualist fixation.

Day time, night time, over time: geographic and temporal uncertainty when linking event and contextual data

Background The growth of geolocated data has opened the door to a wealth of new research opportunities in the health fields. One avenue of particular interest is the relationship between the spaces where people spend time and their health outcomes. This research model typically intersects individual data collected on a specific cohort with publicly available socioeconomic or environmental aggregate data. In spatial terms: individuals are represented as points on map at a particular time, and context is represented as polygons containing aggregated or modeled data from sampled observations. Uncertainty abounds in these kinds of complex representations. Methods We present four sensitivity analysis approaches that interrogate the stability of spatial and temporal relationships between point and polygon data. Positional accuracy assesses the significance of assigning the point to the correct polygon. Neighborhood size investigates how the size of the context assumed to be relevant impacts observed results. Life course considers the impact of variation in contextual effects over time. Time of day recognizes that most people occupy different spaces throughout the day, and that exposure is not simply a function residential location. We use eight years of point data from a longitudinal study of children living in rural Pennsylvania and North Carolina and eight years of air pollution and population data presented at 0.5 mile (0.805 km) grid cells. We first identify the challenges faced for research attempting to match individual outcomes to contextual effects, then present methods for estimating the effect this uncertainty could introduce into an analysis and finally contextualize these measures as part of a larger framework on uncertainty analysis. Results Spatial and temporal uncertainty is highly variable across the children within our cohort and the population in general. For our test datasets, we find greater uncertainty over the life course than in positional accuracy and neighborhood size. Time of day uncertainty is relatively low for these children. Conclusions Spatial and temporal uncertainty should be considered for each individual in a study since the magnitude can vary considerably across observations. The underlying assumptions driving the source data play an important role in the level of measured uncertainty.

Perception Versus Reality: Subjective and Objective Neighborhood Characteristics and Cognitive Function in REGARDS

Does the world shrink as we age? The neighborhood captures a spatial area someone inhabits and moves through on a daily basis. It reflects a balance between internal perceptions and abilities, and the external environment which may enable or restrict participation in everyday life. We frequently hear that older adults have shrinking neighborhoods given declining functional mobility. This is associated with declines in physical and cognitive functioning, depression, poorer quality of life, and mortality. Knowledge of the interplay between objective and subjective neighborhood measurement remains limited. This symposium will explore these linked yet distinct constructs based on secondary data analyses of the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, a racially diverse sample of 30,000+ aging Americans. Finlay investigates how someone’s perceived neighborhood size (in number of blocks) varies by individual and geographic characteristics including age, cognitive function, self-rated health, and urban/rural context. Esposito’s analyses focus on neighborhood size in relation to race and residential segregation. Clarke compares subjective perceptions of neighborhood parks and safety from crime to objective indicators, and examines variations by health and cognitive status. Barnes will critically consider implications for how older adults interpret and engage with their surrounding environments. The symposium questions the validity of neighborhood-based metrics to reflect the perspectives and experiences of older residents, particularly those navigating cognitive decline. It informs policy-making efforts to improve physical neighborhood environments and social community contexts, which are critical to the health and well-being of older adults aging in place.