1. Friends and social networks

6. Unbalanced triad Balance theory Romeo Juliet Capulet - + + Romeo Juliet Capulet + + + Balanced Romeo Juliet Capulet - - + Balanced Romeo Juliet Capulet - + - Balanced

8. Transitive Triads Intransitive Triads Balance theory A D E + + + A D E - - + A D E - - - A D E - + +

9. ? W. Virginia Caucus: On the 2 nd round of balloting, McCain’s supporters voted for Huckabee

12. But balance can produce groups Balance theory Trick: find the triads D I A B E C G J F H

13. Balance theory ---> ---> Friends with Enemies with + - A D E + + + A B E + - - B I E - - + B D I A E - - - - + + + +

14. Balanced Opposition Friends with Enemies with D A B E C G J F H Balance theory I