Sam Gentle.com

Spaced propaganda

I was thinking today about the way that reposts survive on sites like Reddit. You might think that there's no value in posting something that's already been posted earlier, and thus the existence of reposts reveals a flaw in the ranking system in some way. However, I'm not convinced this is necessarily the case.

Firstly, people can sometimes appreciate being reminded of something, like an old joke that you've forgotten still makes you laugh when you hear it again. I'd call that individual forgetfulness. But there's also a second kind: over time new users join the site, older users drift away, and often users will miss new content as it comes in. The result is that even if individuals had perfect memory, the group would lose information. I'd call that population forgetfulness.

We have a fairly robust system for managing individual forgetfulness: spaced repetition. You repeat each thing you want to remember on an exponential scale with an exponent that you adjust for each item depending on how difficult it is to remember. This is a promising idea for managing population forgetfulness; could we generalise it to groups?

To do that you'd first need a way to effectively measure how well the population remembers something. For something like Reddit, you could possibly rely on the repost's score. In the more general case, you could probably use a sampling technique and survey people on their memories. Either way, you'd then need some extra statistical trickery to turn that into the right factor for your spaced repetition exponent. Presumably the tuning would then look like targeting a certain confidence interval of remembering.

Anyway, it occurs to me that once you start thinking about the more general problems you can solve, a lot of them turn out to be pretty unsavoury. For example, how often you should show someone an ad seems like it would be modelled fairly well by population spaced repetition. Similarly, how often should you repeat a message as a repressive government in order to indoctrinate people? I guess it would work for that too.

Well, hopefully it can be used more for good than for evil. Or, if not, I hope we come up with some decent defenses against it.