• Perceived intergroup competition
  
• Social identity theory 
  
• Social judgment
  
• Group-based social hierarchy
  
• Group attribution error 
• Deindividuation
  
• Group polarization 
  
• Integrative theory of intergroup conflict
  
• Perceived group competition
  
• Social comparison
  
• Upward social comparison 
  
• Downward social comparison
  

"Groupthink is a deterioration of mental efficiency, reality testing, and moral judgment that results from in-group pressures." 

        Irving Janus, 1972

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Group Influence
People change their behavior or attitudes to match those of the group they identify with or seek to belong to. Group members often prematurely seek consensus, influencing decisions and actions. 

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Group Polarization
The original attitudes of individuals become exaggerated when shared by others. Group members can fuel each other’s sense of superiority, dislike for adversaries and outrage at any perceived threat. In extreme cases, this exaggerated polarization can lead to group frenzy and mob behavior.

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In-Group Bias 
Identification with a group makes individuals unduly subject to being influenced by the biases, loyalties, and values of the group. Embedding reporters with troops during a war builds ties of loyalty and identification that make it almost impossible for them to report in an impartial or comprehensive way.

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Group Projection
Each “side” projects traits onto the groups that it sees as allies or foes. Two polarized sides call each other biased and extreme. Each may truly believe that the other is being unreasonable. Semantics can blur the line. Freedom fighter or violent rebel? Terrorist or soldier? Fanatic or martyr?

Bandwagon Effect    

Tendency to do (or believe) things because many other people do (or believe) the same. Related to groupthink, herd behavior and conformity.    

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