A theme I’ve been mulling over lately is the question of how unique we really are… More specifically, what set of characteristics makes us really unique?
A simple example: my name is not unique- or at least I don’t think so, though the first five pages of a google search on my name seems to bring up nobody else? Anyway, in general, the first and last name of a person are not unique.
A more advanced example: consider all the playlists of songs – the iTunes Music Store lists 1.421.247 public iMixes at this moment, and almost 7 million votes on those playlists. I suspect that there are no two identical iMixes. (If you know how we could check this, then please do let me know in the comments or by email!) I suspect that my playlists (public as iMixes or private) are unique for me.
Let’s make this a bit more complicated. Take my listening history: probably, if you only consider the last song I listened to, then that is not very unique. There must be other people for whom this is the last song they listened to. Take the last two songs: there may still be other people for whom these are the last songs they listened to. But there must be a number n that makes me unique: there would be no other person that listened to the same last n songs.
I’ve started to refer to such a number as the snowflake number: it is the lowest number of items to consider that makes me unique, just like every snowflake in a snowstorm is unique – it is where the snowflake effect starts to play.
Once you start to think about things this way, a whole set of variations come to mind:
- what is the snowflake number for grocery shopping, i.e. what number of items in my shopping cart do you need to take into account to identify it as uniquely my shopping cart?
- what is the snowflake number for travel, i.e. what number of my last trips do you need to consider before you find nobody else with the same sequence of last trips? (Anyone else has BRU-VIE-BRU as the last trip? Probably. And BRU-LHR-MIA-LHR-BRU before? Probably down to a small number of people now? And BRU-LGW-PSA-LGW-LHR-BRU before Miami? Guess I’m unique now?)
- what is the snowflake number for books? Anyone else who just finished “Exit Ghost” – seems like I’m not alone. Anyone else read “Everything is miscellaneous” before that one? I may be unique having that as the last two books I read? In that case, my snowflake number for books is 2. (Do let me know if you share this sequence for the last two books you read!)
As a smart reader, you will have noticed some nice characteristics of snowflake numbers:
- you can either consider the ordered or unordered list of items: if nobody else read those two books in that order, then my ordered snowflake number is 2, but if some have read the same books in another order, then my unordered snowflake number is 3 or higher;
- you can either consider all the items or from last to more recent only: if you consider all the items, then the question becomes how many of the books I’ve ever read you need to consider before you can no longer find anyone else who has read the same books. I suspect that may be more than 10, but doubt that it is more than 30…
The more eccentric your taste or habits are, the lower your snowflake number will be…
This snowflake number is something I’d really like to explore more. Do you have any other suggestions for contexts in which it would make sense? Do you know of any research on this topic? Do you know how we could compute this for interesting data sets? Do let me know…