 
	The sibling rivalry that divided a town - Jay Van Bavel and Dominic Packer
 In the years before World War Two,
  a pair of brothers worked together
 as shoemakers
  in the German town of Herzogenaurach.
  But during the war, the siblings
 had a terrible argument—
  a fight so explosive it split
 the family business in two.
  At first, the feud only infected 
 their newly competing personnel.
  But over the coming years,
  this disagreement divided
 all of Herzogenaurach.
  Residents became fiercely
 loyal to one brand of shoe.
  Local businesses chose sides and 
 marriage across lines was discouraged.
  Herzogenaurach eventually became 
 known as “the town of bent necks”
  because its residents looked down 
 to ensure they were interacting
  with members of their group.
  But could such a serious divide
 really be about shoes?
  Doesn’t it take more significant 
 cultural differences
  to produce this degree of conflict?
  To answer this question, we can turn 
 to social psychologist Henri Tajfel
  and his collaborators 
 at the University of Bristol.
  This team developed 
 the minimal group paradigm,
  a methodology designed to investigate
  the minimal conditions required 
 to turn people against each other.
  Their plan was to gather participants 
 without the usual factors
  that lead to hostility,
  such as religious, ethnic, 
 gender, or other cultural differences.
  Then, they would split into groups,
  and run them through scenarios
 that added one variable at a time
  to see what stirred up conflict.
  But first, they needed
 a control condition—
  a pair of groups without any group bias.
  The researchers told participants
 they were being grouped
  based on their ability to estimate things
 correctly or incorrectly;
  but in reality, 
 the groups were totally random.
  Since the researchers ensured none
 of the participants interacted,
  no one could form any judgments
 or personal bonds.
  Then everyone was given resources
 to distribute.
  Each participant was free to give
 resources to members of either group,
  and importantly, everything was anonymous.
  So whatever a participant decided,
  it had no impact on how many resources
 they personally would receive.
  With all the ingredients 
 for discrimination removed
  and no reason for competition
 over resources,
  the scientists assumed this would
 make a conflict-free baseline
  for further research.
  But even in these groups,
  where membership was only defined 
 by a perceived similarity
  in possessing an arbitrary skill,
  individuals still showed in-group bias.
  They consistently gave more to members
 of their own group than the out-group.
  Later, research went even further,
  informing participants that the only thing
 determining their group membership
  was a coin flip.
  But group bias still occurred.
  The minimal groups of “us” and “them”
 were enough.
  So, in the absence of stereotypes, 
 resource conflicts and status differences,
  what was left?
  What could possibly account for people 
 showing clear preferences
  for the most temporary and meaningless
 of groups?
  The answer that came to Tajfel 
 and his colleagues was social identity.
  People regularly use group membership 
 to help determine their sense of identity.
  And these minimal group experiments
 suggested that simply being categorized
  as part of a group is enough to link 
 that group to a person’s sense of self.
  Then, in an effort to create
 a meaningful identity,
  participants allocated more resources
 to their in-group than the out-group—
  pursuing their group's interests despite
 no clear benefit to themselves
  as individuals.
  Variants of these experiments have 
 been conducted around the globe,
  examining how a shared sense 
 of “us” can affect our attention,
  perception, memory, and emotions.
  The mental processes
 behind minimal group distinctions
  appear to be the same as many of those
 that underlie real group identities.
  So it is possible that these seemingly
 insignificant differences can harden
  into much more serious divides.
  That said, minimal groups don't
 always drive people apart.
  Bringing individuals together 
 in a new group
  can temporarily help people
 overcome entrenched biases.
  However, these positive effects are easily
 negated by external factors
  that reinforce existing group identities.
  Ultimately, the psychology of groups
 is part of the human condition,
  and our tendency towards in-group bias
 is an undeniable part of that.
  So it's up to all of us to make
 our groups and ourselves
  as inclusive of others as possible.