Big Brother and Alliance Networks

Big Brother is a show televised on CBS each summer. Players live in a house together and compete to win a half million dollar prize, and there are 16 contestants typically competing to win the prize. Typically, one person is the “head” of the house for a week, nominates 2 people for eviction, the contestants have a chance to compete to possibly ‘save’ themselves, and then there is a vote in which one person is “evicted” from the house each week.

The alliance networks of Big Brother are particularly interesting. It’s a game of back-stabbing, numbers, and strategy all into one. Who you make friends with matters, as your friends may turn you into a target. As the numbers dwindle and the game becomes smaller and smaller, people typically have an idea of where they stand, but there’s always a chance of betrayal, which leads to paranoia and conflict between the houseguests. In a game like Big Brother, cascading information also commonly occurs. Rumors can easily be conceived as truth, particularly given paranoia levels.

Here are the alliance networks from one game of Big Brother as it evolved throughout:

On the second day in the house, Brian, Dan and Ollie make an alliance. Brian then goes and makes an alliance with Jerry, which blows up in his face and results in a mega-alliance between the members below, with only Dan staying by Brian’s side. Brian is then evicted.

On Day 10, some members of the 8 person alliance realized that the 8 person alliance could not survive — and decided to create their own.

On Day 13, the other 4 members of the 8 person alliance decided to create their own alliance. As we can see here, there are now 2, 4 person alliances, and 3 “floaters” left in the game — players who have no alliances and are often picked off.

On Day 26, a key vote emerged — Memphis and Jessie were up for eviction, and the house was divided into two camps. With the vote clearly deadlocked at 3-3… the deciding vote was clearly on Dan. However, a twist put into the game earlier that week ensured his vote was up in the air and controlled by the viewers, and not him…


On day 35 in the house, Dan and Memphis make a “Final 2” deal. This is about the most serious deal you can make in the house, as you are promising to go to the end with one another… and something, that if betrayed, often leaves others very bitter.


On Day 39, the power dynamic had evolved as follows… Ollie/Michelle/April were aligned, Renny/Dan/Memphis/Keesha were aligned, and Jerry was a “floater”.


On Day 51, as the odd one out, Jerry grabs power. Memphis aligns himself with Jerry to help protect Dan and himself… which eventually leads to Dan and Memphis successfully controlling the vote and evicting Renny.

In Day 58, Dan and Memphis decide to flip on Keesha and evict her out of the house. On the left is how Keesha perceived the alliances, whereas on the right was how the alliances actually were aligned. Keesha is then evicted.

Dan and Memphis then initiate a big fight between themselves, to trick Jerry into thinking that he is going to win and to lull him into a sense of complacency. Their trap works and Dan wins the final “head” of household, leading him to evict Jerry and to make it to the final vote with him and Memphis.


The jury (a group of 9 houseguests) then vote for who they think should win — and it is unanimous — Dan wins.