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Modeling Opinion Flow in Humans Using Boids Algorithm & Social Network Analysis
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Modeling Opinion Flow in Humans Using Boids Algorithm & Social Network Analysis

September 28, 2006 Article Start Previous Page 4 of 8 Next

Allowing Opinions to Change

Now that we have create a way to determine the force on an actor pulling him or her in a particular direction, it is time to allow the actors to actually move in their opinions.

The force we calculated will be used to generate a probability that the individual moves in his or thinking in one way or another. The proportionality constant we use will need to be selected to provide realistic movement in the opinions in the actors.

Probability of Change of Opinion = proportionality constant * Force

We will propagate this effect through multiple rounds. Each time step we will calculate the forces on each individual, and determine if this leads them to move in their opinion5.

The ‘time step’ selected can be any one desired (daily, weekly, monthly, etc.). The probabilities to change should roughly correlate with the time scale, and the profundity of the topic at hand. It’s not likely that most individuals re-assess deeply held beliefs daily, but they may monthly or yearly. If the topic at hand is not deep (should I sell off my overvalued Internet stock) then that is a decision that can be checked more frequently.

Basic Technique

  • Create a population of ‘person’ objects.
    • May be a population of one or more types of actors.
    • You may want to enter details about the characteristics (composition) of the various actors.
  • Establish and normalize the linkages amongst the population members.
    • Create random connections between actors.
    • Randomly assign the strength of the connections. A positive number indicates that the first actor respects the second actor. A negative number indicates contempt.
    • Normalize the connections so their sum total equals 1.
  • Establish the initial alignments (the opinion regarding the topic at hand).
  • Loop over all individuals
    • For each individual, calculate the forces acting on them.
    • Based on the forces, determine randomly if the person changes in their alignment.
  • Repeat step 4 at each time step in the game.

How far an actor moves when they do change opinion is an interesting question. In real life any distance is possible. For the purpose of the game simulation, we will just say that when an actor moves, her or she will move one unit in the direction of the weighted average that they see around them.

Whether or not someone overshoots the crowd average and becomes a radical is really more a question of their composition. Are they someone who is ready to become a radical? The number of people ready for radicalization in a society can be something the game creator enters, and have these people respond differently to movements in thought - they will take things to an even higher level.

How the Player Interacts with All of This

We have created a system, like a school of fish swimming in a pool, that can move and fluctuate on its own. This is interesting, but of course the game will be in the player trying to direct that movement. King Richard wants people to accept that he is the rightful king. People advocating a particular idea, such as universal suffrage or democracy, want other people to accept that idea.

In some cases, the player may choose to interact ‘up close and personal’ with those who disagree with their point of view. A game creator could create a population of 1000 people in which 10 of these people will continually strive to thwart the player. The game could be for the player to locate and convince the spoilers (with a flame thrower or rocket propelled grenade) to stop trying to thwart him. Note: collateral damage may have adverse affects.

Other, subtler, techniques can also be made available to the player. A partial list of possibilities is given below. You may think of others.



Providing Aid

Someone is more inclined to believe someone for whom they have frequent contact and respect. Providing Aid is a way of establishing a good relationship. This can fail if it is perceived as trying to ‘buy affection’ but if done correctly it can help move a population over to your side.

Disgracing Opponent

If a player can change the respect that the non-player characters have for a spoiler into contempt, then one can effectively reverse their affect. If they can destroy the credibility of their opponent, they can mitigate their influence.


A specific event in characters life (for example, seeing the fall of the Berlin Wall, or seeing their parents murdered) can have profound influence on their views. But.. (and this is a very large ‘but’)
What generally matters more than an event is how that event is translated via the news services (see “News” below)


Courses can be used to affect the way people believe.


How news arrives also greatly influences its affect.
The same news (the ownership of a castle has changing hands) could presented as “The murderous and villainous forces of King Richard have via treachery taking castle x” or “King John's weak and ill-fed forces where no match to the superior might of King Richard's noble lancers.”
The player can influence which news reaches the bulk of the population. Obviously, news has to come from a respected source for it to have much weight.


Termination or Incarceration of the enemy actor.

Table 4. Methods in which the player may interact to change opinions in the population of actors.

Article Start Previous Page 4 of 8 Next

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