Sunday 14 November 2010

Twitter transitivity and identity

I tweet via @EricCrampton.

The new Twitter interface gives a list of folks similar to me. Or, at least it lists four different ones each time I refresh.

The first one that came up is @Offsetting. That's good. That's the account I use for tweeting posts from the blog. So it should be similar to me - it is me. I am similar to me. Twitter has proven identity. Good start.

Transitivity gets harder though.

I am similar to @wtdickens. Maybe a bit - he's a hell of a lot smarter than I am. I'm his Grandstudent via Bryan Caplan.

But @wtdickens is similar to @SFFedReserve, @stlouisfed, and @clevelandFed. Bill's a serious macro guy, so I can see how he'd be similar to a Fed. But I'm certainly not similar to a Fed. Transitivity fails.

I'm also similar to @jodiecongirl, who is similar to @Nudgeblog. Again, transitivity fails.

I wonder if there's any back end list of all the folks on your "similar to" list and their propensity scores (or whatever they're using for a matching algorithm).


  1. Couldn't this be a result of the second and third party having greater similarity among the traits that the first and second party have little similarity in?

    For example, you're very similar (relative to the rest of the population) to both of your parents, but your parents may not be all that similar to each other.

  2. What Henry said. "Similarity" isn't something you expect to be transitive, like preference.

  3. So we don't expect it to be transitive and we find it isn't transitive. Useful test.