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## WHAT IS IT?
This is an implementation of the Hierarchical Ising Opinion Model (HIOM).
van der Maas, H. L. J., Dalege, J., & Waldorp, L. J. (2020). The polarization within and across individuals: The hierarchical Ising opinion model. Journal of Complex Networks, 8, cnaa010.
The opinion of agents is modeled by a stochastic (cusp) differential function in which attention and information are the control variables of the cusp. Agents interact and influence both attention and information. Due to hysteresis within agents, this leads to new explanations of polarization.
The cusp model of the individual is derived from the Ising attitude model, described in
Dalege, J., & van der Maas, H. L. J. (2020). Accurate by being noisy: A formal network model of implicit measures of attitudes. Social Cognition, 38, S26-S41.
Dalege, J., Borsboom, D., van Harreveld, F., & van der Maas, H. L. J. (2019). A network perspective on attitude strength: Testing the connectivity hypothesis. Social Psychological and Personality Science, 10, 746-756.
Dalege, J., Borsboom, D., van Harreveld, F., & van der Maas, H. L. J. (2018). The Attitudinal Entropy (AE) Framework as a General Theory of Individual Attitudes. Psychological Inquiry, 29, 175-193.
Dalege, J., Borsboom, D., van Harreveld, F., van den Berg, H., Conner, M., & van der Maas, H. L. J. (2016). Toward a formalized account of attitudes: The Causal Attitude Network (CAN) model. Psychological Review, 123, 2-22.
## HOW IT WORKS
The algorithm has been slightly changed
Iterate
* Randomly choose a set of agents, weighted with attention A (modified eq. 5).
(4) dO<sub>i</sub> = -(O<sub>i</sub>^3-(A<sub>i</sub>+A_min)O<sub>i</sub>-I<sub>i</sub> )dt+s<sub>O</sub> dW<sub>i</sub> (t)
Where dt = .01, Amin = -.5
O is opinion, A is attention, I is information
and parameters (set by sliders):
## HOW TO USE IT
SETUP sets the agents to values determined by mean-init-information, sd-init-information, mean-init-attention, sd-init-attention.
The sliders set parameters of the main equations for attention, information, and opinion (see HOW IT WORKS).
Visualize can be set to opinion, attention, information.
The histograms show the distribution of opinion, attention and information.
setup-black-pete is used to set the parameters to the value required for the Black-Pete simulation described in the HIOM 2021 paper. In this scenario, activists are added to a conservative community with low attention. If attention grows too quickly, polarization will result. Click on add-activist to allow activists to be added with mouse clicks.
setup-meat-eating-vegetarian is used to set the parameters to the value required for the meat-eating vegetarian simulation described in the HIOM 2021 paper. In this simulation, the bound is set low, meaning that agents that are too different will not interact.
## THINGS TO NOTICE
Polarization due to hysteresis (simulation 1 in the HIOM paper):
In the standard setup, you can see that high attention (set %active-agent high) leads to polarization. If you now decrease the difference in information (set decay_I to .5), the polarization remains even if the difference in underlying information is 0. Only if you also decrease attention (set %active-agents low), the polarization disappears.
Opposition to activism: the case of Black Pete (simulation 2 in the HIOM paper):
A solution to polarization: the meat-eating vegetarian (simulation 3 in the HIOM paper):
## THINGS TO TRY
The mean noise information function as an external field. Test if varying this paramter gives hystersis at the level of the mean opionion over agents.
Test the robustness of the 3 simulations by adjusting model parameters with the sliders.
In the Black Pete simulation activist are more succesful when attention changes slowly. Adjust da and %active-agents to test this.
In the meat-eating vegetarian simulation, the pertubation only works when attention is relatively low. Test this by setting %active-agents high.
## EXTENDING THE MODEL
Set-up the model in a preferential atttachment network
## CREDITS AND REFERENCES
van der Maas, H. L. J., Dalege, J., & Waldorp, L. J. (2020). The polarization within and across individuals: The hierarchical Ising opinion model. Journal of Complex Networks, 8, cnaa010. |
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