Putting the Sex in SNA: Hook up Networks

Imagine you are a network scientist meeting new people in a bar. At one point, there is always the question: "So what is your research topic?". Shocked and horrified, you are looking for an answer that does not scare away your new acquaintance. "algorithmic graph theory"? Sounds to nerdy. "social network analysis" ? Sounds better but you are tired of explaining that this is not the same as browsing facebook all day. Maybe an example from your work! "Protein Interaction Networks"? Oh god i had too many beers to explain that. 

Hook up Network of Grey's Anatomy

For the described situation, it is always good to have an example ready that is relevant in real life.
And what could be more relevant than talking about "hook up networks". Yes that's a thing and you CAN do serious research with them. Or use them as a pick up line. 
     




The first time I stumbled upon these kinds of networks was when i was looking for an interesting example to show some basic network modeling approaches in a class. What I found was the "who slept with whom" network of Grey's Anatomy [1,2]. Everybody who is familiar with that show will agree that besides hospital stuff, there is a lot of hanky-panky going on.

Below you find a visualization of the network, where the node size is proportional to the number of hook ups.




Comparing Grey's Anatomy with the "real world"

Reddit user /u/kreekkrew had a fascinating project during his time in college. He recorded every hook up within his group of friends and published this matrix with the following explanation:
"This shows who has made out with who in my group of friends over the course of my time in college.
Criteria for data collection:
1. To be on the chart, a person needs to have been to at least two of our parties since my freshman year (2010).
2. For a make-out session to count, it needs to:
Population is composed of 26 people (61% male/39% female), aged between 18 and 24, all at an engineering school (believe it or not) in the US. Obviously, names have been initialized for the sake of privacy."

Of course, I turned his matrix into a network


Now we can compare how Grey's Anatomy relates to the real word (as real as engineering school gets...) The table shows some simple statistics for both networks.



Most of the statistics should be self explanatory, except maybe the 4-cycle statistic.

A study on sexual networks [3] found a prohibition against coupling with a former partner’s former partner’s former partner (a 4 cycle) due to status implications. That is, counting 4 cycles allows us to quantify a level of potential drama, since awkward status implications arising from other’s sexual relationships make for compelling entertainment.

What do we learn?

Engineering school is far more dramatic than Grey's Anatomy (compare 4 cycles). To make Grey's Anatomy a bit more realistic, they should maybe implement some more same sex coupling. I guess "McDreamy" hooking up with another male doctor would create quite some confusion among the female viewership. 

And poor dudes at Engineering school. Females are already quite rare there (Which is itself quite sad!), and the few that go there decide to rather make out with each other...

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