Opinion Cascades and Echo-Chambers in Online Networks: A Proof of Concept Agent-Based Model

In online networks, the polarization of opinions (e.g., regarding presidential elections or referenda) has been associated with the creation of “echo-chambers” of like-minded peers, secluded from those of contrary viewpoints. Previous work has commonly attributed such phenomena to self-regarding preferences (e.g., confirmation bias), individual differences, and the pre-dispositions of users, with clusters forming over repeated interactions. The present work provides a proof of concept Agent-Based Model that demonstrates online networks are susceptible to echo-chambers from a single opinion cascade, due to the spatiotemporal order induced by lateral transmission. This susceptibility is found to vary as a function of degree of interconnectivity and opinion strength. Critically, such effects are found despite globally proportionate levels of opinions, equally rational agents (i.e. absent conformity, confirmation bias or pre-disposition architecture), and prior to cyclical interactions. The assumptions and implications of this work, including the value of Agent-Based Modelling to cognitive psychology, are discussed

Bistable Helmholtz dark spatial optical solitons in materials with self-defocusing saturable nonlinearity

We present, to the best of our knowledge, the first exact dark spatial solitons of a nonlinear Helmholtz equation with a self-defocusing saturable refractive-index model. These solutions capture oblique (arbitrary-angle) propagation in both the forward and backward directions, and they can also exhibit a bistability characteristic. A detailed derivation is presented, obtained by combining coordinate transformations and direct-integration methods, and the corresponding solutions of paraxial theory are recovered asymptotically as a subset. Simulations examine the robustness of the new Helmholtz solitons, with stationary states emerging from a range of perturbed input beams

Multivariable Predictors of MVPA in Sport, All Episodes.

<p>¹⁾ Binary: 1 if better-educated parent entered college, 0 if not.</p><p>²⁾ Activity levels as described in [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135630#pone.0135630.ref024" target="_blank">24</a>]. MVPA is moderate or vigorous physical activity and refers to non-sporting days only. Participants with sport every day (9, 1.4%) are missing.</p><p>³⁾ Team sport defined as any requiring interaction with other participants, in line with [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135630#pone.0135630.ref021" target="_blank">21</a>]</p><p>N/A = P ≥0.05 so predictor was removed from the model.,— = not included in initial model</p><p>Predictors above the double line (age, study center, parental education, and gender; episode length when predicting zero MVPA, but not when predicting nonzero MVPA) left in model regardless of statistical significance. Nonzero MVPA modeled with negative binomial regression with log of total sporting time as offset, zeroes with logistic regression, both with child as a repeated measure.</p><p>Multivariable Predictors of MVPA in Sport, All Episodes.</p

Engagement in Sports with 9 or Fewer Episodes for Both Sexes.

<p>Activity levels as described in[<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135630#pone.0135630.ref024" target="_blank">24</a>]. MVPA is moderate or vigorous. Moderate + vigorous may not sum to MVPA because of rounding. Team sport defined as any requiring interaction with other participants, in line with [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135630#pone.0135630.ref021" target="_blank">21</a>].</p><p>Engagement in Sports with 9 or Fewer Episodes for Both Sexes.</p

Engagement in Sports with 10 or More Episodes for at Least One Sex.

<p>Activity levels as described in[<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135630#pone.0135630.ref024" target="_blank">24</a>]. MVPA is moderate or vigorous. Moderate + vigorous may not sum to MVPA because of rounding. Team sport defined as any requiring interaction with other participants, in line with [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135630#pone.0135630.ref021" target="_blank">21</a>].</p><p>Engagement in Sports with 10 or More Episodes for at Least One Sex.</p

Time in MVPA During Sport.

<p>MVPA as determined in Freedson‘s accelerometric algorithm (Freedson et al 2005, #19). Sports shown if that sex had >10 episodes during recording. Error bars for standard error of the mean.</p

Daily Activity in German Adolescents.

<p>PE is any time between diaried start and end of school physical education (PE.) School is any time between diaried start and end of school, outside PE. Leisure Sport is any time outside of PE when the subject diaries sport. Transport is time between leaving home and arriving at school. Only the trip to school is described. Other is all other waking time when the monitor was worn. Estimates for PE and Leisure Sport include estimated moderate and vigorous activity during this period if the diary shows the device was not worn due to sport such as swimming. Calculations are based on data applying Freedson‘s vertical-axis algorithm for children from Freedson et al, 2005 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0152217#pone.0152217.ref033" target="_blank">33</a>] as cited in [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0152217#pone.0152217.ref037" target="_blank">37</a>]. MVPA is moderate + vigorous physical activity.</p

Activity Allocation by Domain, All Days.

<p>Activity Allocation by Domain, All Days.</p

Accelerometry Response Rate.

<p>GINIplus15 and LISAPlus15 are the 15-year followups of birth cohorts GINIplus and LISAPlus. For details on GINIplus and LISAplus see von Berg et al, 2003 and 2015 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0152217#pone.0152217.ref024" target="_blank">24</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0152217#pone.0152217.ref026" target="_blank">26</a>]and Chen et al, 2007 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0152217#pone.0152217.ref019" target="_blank">19</a>] respectively. We give the number and percentage of subjects as a percentage of those contacted for accelerometry, those who gave their consent, and those who completed accelerometry and returned the device. Quality control failure includes inconsistency between diary and weartime criteria of Troiano et al, 2007 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0152217#pone.0152217.ref027" target="_blank">27</a>] using SAS programs published by NHANES [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0152217#pone.0152217.ref028" target="_blank">28</a>](58% of excluded days); other non-wear time issues (27% of excluded days); and technical issues (7.4% of excluded days). Many days were invalid for more than one reason.</p

Population Characteristics and Selection.

<p>Population Characteristics and Selection.</p