Optimizing Opinions with Stubborn Agents

We consider the problem of optimizing the placement of stubborn agents in a social network in order to maximally influence the population. We assume the network contains stubborn users whose opinions do not change, and non-stubborn users who can be persuaded. We further assume the opinions in the network are in an equilibrium that is common to many opinion dynamics models, including the well-known DeGroot model. We develop a discrete optimization formulation for the problem of maximally shifting the equilibrium opinions in a network by targeting users with stubborn agents. The opinion objective functions we consider are the opinion mean, the opinion variance, and the number of individuals whose opinion exceeds a fixed threshold. We show that the mean opinion is a monotone submodular function, allowing us to find a good solution using a greedy algorithm. We find that on real social networks in Twitter consisting of tens of thousands of individuals, a small number of stubborn agents can non-trivially influence the equilibrium opinions. Furthermore, we show that our greedy algorithm outperforms several common benchmarks. We then propose an opinion dynamics model where users communicate noisy versions of their opinions, communications are random, users grow more stubborn with time, and there is heterogeneity is how users' stubbornness increases. We prove that under fairly general conditions on the stubbornness rates of the individuals, the opinions in this model converge to the same equilibrium as the DeGroot model, despite the randomness and user heterogeneity in the model.Comment: 40 pages, 11 figure

Adaptation: Market Sector Responses, Scott Hunter

Adaptation: Market Sector Responses Panelists will share information on new business opportunities evolving out of recurrent flooding occurrences, new renovation loan solutions, and innovative financing opportunities

Hunter Berbrich Honors Portfolio

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Psychopathology In Adolescents With A History Of Foster Care

Despite the enormous cost of the foster care system, high rates of psychopathology and homelessness among young-adult foster care alumni provide a stark reminder of the challenges faced by this vulnerable population. This study characterizes the effect of a history of foster care on psychopathology in a group of 39 adolescents that had exited foster care and were reunified with their biological mothers. A history of foster care was defined as out-of-home placement by child welfare for at least one month; median foster stay was 1.5 years and median age at placement was 8.5 years. A control group of 78 adolescents was matched with the foster group using exact and logistic-regression nearest-neighbor methods. Matched variables included well-established, major childhood risk factors for the development of psychopathology: maternal substance abuse, maternal psychopathology, and childhood maltreatment (i.e. physical and sexual abuse, neglect and domestic violence). With the two groups matched in this way, recent research suggests that the two groups had comparable histories of adverse childhood events, and thus the major inter-group difference is a temporary separation from the biological mother, enforced by child welfare services (i.e foster care). Participants, and their mothers as second reporters, completed self-report, parent-report and structured interview assessments, providing data on major psychiatric diagnoses and symptom scales. The prevalence of externalizing diagnoses in the foster group was 41.0% (24.9% - 57.2%) compared with 19.2% (10.3% - 28.2%) in the control group (r = .25). Substance dependence prevalence was 25.6% (11.3% - 40.0%) compared with 5.1% (0.1% - 10.1%) in the control group (r = .30). The foster group also had more depression symptoms as measured by three assessments (p \u3c .05, r = .21 to .25); the foster group also had more overall externalizing symptoms (p = .015, r = .22), including conduct problems (p = .007, r = .25) and hyperactivity (p = .023, r = .21). For every comparison made, the foster group demonstrated more psychopathology than controls. Thus despite the protective goal of foster care, it may have detrimental effects on the child\u27s subsequent development. Further studies with larger sample sizes are needed to confirm these findings that have the potential to substantially alter child welfare policy by reducing the number of foster care placements in favor of other child and family support services

Anchoring and Adjusting in Questionnaire Responses

When ordering items on attitude/opinion questionnaires, do survey designers bias respondents’ answers by the mere act of choosing to organize their survey in a particular way? We hypothesize that, under specific frequently-occurring conditions, respondents employ an anchoring and adjusting strategy in which their response to an initial survey item provides a cognitive anchor from which they (insufficiently) adjust in answering the subsequent item. Three experiments indicate that respondents anchor and insufficiently adjust in certain situations, anchoring and adjusting leads to higher inter-item correlations between adjacent items, and these inflated correlations can (spuriously) increase the reliability estimate of the scale that they comprise and affect the resultant correlations with other measures. These effects are not consistently accounted for by a “superior memory search” explanation. In organizing their surveys, researchers may wish to combat this bias by intermixing items designed for different, but related constructs

Using the Theory of Satisficing to Evaluate the Quality of Survey Data

Increasingly colleges and universities use survey results to make decisions, inform research, and shape public opinion. Given the large number of surveys distributed on campuses, can researchers reasonably expect that busy respondents will diligently answer each and every question? Less serious respondents may 'satisfice,' i.e., take short-cuts to conserve effort, in a number of ways-choosing the same response every time, skipping items, rushing through the instrument, or quitting early. In this paper we apply this satisficing framework to demonstrate analytic options for assessing respondents' conscientiousness in giving high fidelity survey answers. Specifically, we operationalize satisficing as a series of measurable behaviors and compute a satisficing index for each survey respondent. Using data from two surveys administered in university contexts, we find that the majority of respondents engaged in satisficing behaviors, that single-item results can be significantly impacted by satisficing, and that scale reliabilities and correlations can be altered by satisficing behaviors. We conclude with a discussion of the importance of identifying satisficers in routine survey analysis in order to verify data quality prior to using results for decision-making, research, or public dissemination of finding