The Final Volume of the Groundbreaking Trilogy on Agent-Based Modeling
In this pioneering synthesis, Joshua Epstein introduces a new theoretical entity:Agent_Zero. This software individual, or ..."agent," is endowed with distinct emotional/affective, cognitive/deliberative, and social modules. Grounded in contemporary neuroscience, these internal components interact to generate observed, often far-from-rational, individual behavior. When multiple agents of this new type move and interact spatially, they collectively generate an astonishing range of dynamics spanning the fields of social conflict, psychology, public health, law, network science, and economics.
Epstein weaves a computational tapestry with threads from Plato, Hume, Darwin, Pavlov, Smith, Tolstoy, Marx, James, and Dostoevsky, among others. This transformative synthesis of social philosophy, cognitive neuroscience, and agent-based modeling will fascinate scholars and students of every stripe. Epstein's computer programs are provided in the book or on its Princeton University Press website, along with movies of his "computational parables."
Agent_Zerois a signal departure in what it includes (e.g., a new synthesis of neurally grounded internal modules), what it eschews (e.g., standard behavioral imitation), the phenomena it generates (from genocide to financial panic), and the modeling arsenal it offers the scientific community.
For generative social science,Agent_Zeropresents a groundbreaking vision and the tools to realize it.
We demonstrate that individual behaviours directed at the attainment of distinctiveness can in fact produce complete social conformity. We thus offer an unexpected generative mechanism for this ...central social phenomenon. Specifically, we establish that agents who have fixed needs to be distinct and adapt their positions to achieve distinctiveness goals, can nevertheless self-organize to a limiting state of absolute conformity. This seemingly paradoxical result is deduced formally from a small number of natural assumptions and is then explored at length computationally. Interesting departures from this conformity equilibrium are also possible, including divergence in positions. The effect of extremist minorities on these dynamics is discussed. A simple extension is then introduced, which allows the model to generate and maintain social diversity, including multimodal distinctiveness distributions. The paper contributes formal definitions, analytical deductions and counterintuitive findings to the literature on individual distinctiveness and social conformity.
The development of attention-deficit/hyperactivity disorder (ADHD) care quality measurements is a prerequisite to improving the quality of community-based pediatric care of children with ADHD. ...Unfortunately, the evidence base for existing ADHD care quality metrics is poor. The objective of this study was to identify which components of ADHD care best predict patient outcomes.
Parents of 372 medication-naïve children in grades 1 to 5 presenting to their community-based pediatrician (N = 195) for an ADHD-related concern and who were subsequently prescribed ADHD medication were identified. Parents completed the Vanderbilt ADHD Parent Rating Scale (VAPRS) at the time ADHD was raised as a concern and then approximately 12 months after starting ADHD medication. Each patient's chart was reviewed to measure 12 different components of ADHD care.
Across all children, the mean decrease in VAPRS total symptom score during the first year of treatment was 11.6 (standard deviation 10.1). Of the 12 components of ADHD care, shorter times to first contact and more teacher ratings collected in the first year of treatment significantly predicted greater decreases in patient total symptom scores. Notably, it was timeliness of contacts, defined as office visits, phone calls, or email communication, that predicted more ADHD symptom decreases. Office visits alone, in terms of number or timeliness, did not predict patient outcomes.
The magnitude of ADHD symptom decrease that can be achieved with the use of ADHD medications was associated with specific components of ADHD care. Future development and modifications of ADHD quality care metrics should include these ADHD care components.
Objective: This study compared practitioner self-report of ADHD quality of care measures with actual performance, as documented by chart review. Method: In total, 188 practitioners from 50 pediatric ...practices completed questionnaires in which they self-reported estimates of ADHD quality of care indicators. A total of 1,599 charts were reviewed. Results: The percentage of patients for whom practitioners self-reported that they used evidence-based care was higher in every performance category when compared with chart review, including higher use of parent and teacher rating scales during assessment and treatment compared with chart review. Self-reported use of Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV) criteria during assessment was also higher than by chart review. The actual number of days until the first contact after starting medication was nearly three times longer than self-report estimates. Conclusion: Practitioners overreport performance on quality of care indicators. These differences were large and consistent across ADHD diagnostic and treatment monitoring practices. Practitioner self-report of ADHD guideline adherence should not be considered a valid measure of performance.
Long House Valley in the Black Mesa area of northeastern Arizona (U.S.) was inhabited by the Kayenta Anasazi from about 1800 before Christ to about anno Domini 1300. These people were prehistoric ...ancestors of the modern Pueblo cultures of the Colorado Plateau. Paleoenvironmental research based on alluvial geomorphology, palynology, and dendroclimatology permits accurate quantitative reconstruction of annual fluctuations in potential agricultural production (kg of maize per hectare). The archaeological record of Anasazi farming groups from anno Domini 200-1300 provides information on a millennium of sociocultural stasis, variability, change, and adaptation. We report on a multiagent computational model of this society that closely reproduces the main features of its actual history, including population ebb and flow, changing spatial settlement patterns, and eventual rapid decline. The agents in the model are monoagriculturalists, who decide both where to situate their fields as well as the location of their settlements. Nutritional needs constrain fertility. Agent heterogeneity, difficult to model mathematically, is demonstrated to be crucial to the high fidelity of the model.
To examine patient- and provider-level factors associated with receiving attention-deficit/hyperactivity disorder (ADHD) medication treatment in a community care setting. We hypothesized that the ...likelihood of ADHD medication receipt would be lower in groups with specific patient sociodemographic (eg, female sex, race other than white) and clinical (eg, comorbid conditions) characteristics as well as physician characteristics (eg, older age, more years since completing training).
A retrospective cohort study was conducted with 577 children (mean age, 7.8 years; 70% male) presenting for ADHD to 50 community-based practices. The bivariate relationship between each patient- and physician-level predictor and whether the child was prescribed ADHD medication was assessed. A multivariable model predicting ADHD medication prescription was conducted using predictors with significant (P < .05) bivariate associations.
Sixty-nine percent of children were prescribed ADHD medication in the year after initial presentation for ADHD-related concerns. Eleven of 31 predictors demonstrated a significant (P < .05) bivariate relationship with medication prescription. In the multivariable model, being male (OR, 1.34; 95% CI, 1.01-1.78; P = .02), living in a neighborhood with higher medical expenditures (OR, 1.11 for every $100 increase; 95% CI, 1.03-1.21; P = .005), and higher scores on parent inattention ratings (OR, 1.06; 95% CI, 1.03-1.10; P < .0001) increased the likelihood of ADHD medication prescription.
We found that some children, based on sociodemographic and clinical characteristics, are less likely to receive an ADHD medication prescription. An important next step will be to examine the source and reasons for these disparities in an effort to develop strategies for minimizing treatment barriers.
The current study examined predictors of academic achievement, measured by standardized test scores, and performance, measured by school grades, in adolescents (Mn age = 16.8) who met diagnostic ...criteria for Attention-Deficit/Hyperactivity Disorder (ADHD)-Combined type in early childhood (Mn age = 8.5; N = 579). Several mediation models were also tested to determine whether ADHD medication use, receipt of special education services, classroom performance, homework completion, or homework management mediated the relationship between symptoms of ADHD and academic outcomes. Childhood predictors of adolescent achievement differed from those for performance. Classroom performance and homework management mediated the relationship between symptoms of inattention and academic outcomes.
Objective:
Reaction time (RT) variability is often purported to indicate behavioral attention. This study seeks to examine whether RT variability in children with Attention Deficit Hyperactivity ...Disorder (ADHD) is associated with observed behavioral indicators of attention.
Method:
One-hundred 47 participants with and without ADHD completed five computerized neuropsychological tasks and an analog math task. Linear mixed models were utilized to examine the relationship between observations of behavioral inattention during the analog task and measures of RT variability from the neuropsychological tasks.
Results:
Significant associations were observed between RT variability and mean duration of on-task behavior on the analog math task. Secondary analyses indicated that on-task behavior during the math task was also related to accuracy on the neuropsychological tasks.
Conclusions:
RT variability, especially the portion of RT variability characterized by long RTs, appears to measure a cognitive phenomenon that relates to successful on-task academic behavior across children with and without ADHD. The relationship between RT variability and on-task behavior is present across multiple neuropsychological tasks and does not appear to be moderated by age, sex, or the presence of anxiety or depression.
Objective: This study examined neurocognitive and behavioral predictors of math performance in children with and without ADHD. Method: Neurocognitive and behavioral variables were examined as ...predictors of (a) standardized mathematics achievement scores, (b) productivity on an analog math task, and (c) accuracy on an analog math task. Results: Children with ADHD had lower achievement scores but did not significantly differ from controls on math productivity or accuracy. N-back accuracy and parent-rated attention predicted math achievement. N-back accuracy and observed attention predicted math productivity. Alerting scores on the attentional network task predicted math accuracy. Mediation analyses indicated that n-back accuracy significantly mediated the relationship between diagnostic group and math achievement. Conclusion: Neurocognition, rather than behavior, may account for the deficits in math achievement exhibited by many children with ADHD.
While foreign assistance must continue, a nascent local strategy is a candidate for broad adoption. We call it MORE, for MObilization of REcovered individuals. The idea is simple: those who have ...recovered from Ebola could be engaged to reduce transmission, helping to bring the epidemic under control.
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