Tag: trees

Big Data and Fast Frugal Trees

In his excellent podcast episode with EconTalk’s Russ Roberts, psychologist Gerd Gigerenzer introduces the concept of “fast and frugal trees“. When someone needs to make decisions quickly, Gigerenzer says, they don’t take into account a large number of factors, but instead rely on a small set of thumb rules.

The podcast itself is based on Gigerenzer’s 2009 book Gut Feelings. Based on how awesome the podcast was, I read the book, but found that it didn’t offer too much more than what the podcast itself had to offer.

Coming back to fast and frugal trees..

In recent times, ever since “big data” became a “thing” in the early 2010s, it is popular for companies to tout the complexity of their decision algorithms, and machine learning systems. An easy way for companies to display this complexity is to talk about the number of variables they take into account while making a decision.

For example, you can have “fin-tech” lenders who claim to use “thousands of data points” on their prospective customers’ histories to determine whether to give out a loan. A similar number of data points is used to evaluate resumes and determine if a candidate should be called for an interview.

With cheap data storage and compute power, it has become rather fashionable to “use all the data available” and build complex machine learning models (which aren’t that complex to build) for decisions that were earlier made by humans. The problem with this is that this can sometimes result in over-fitting (system learning something that it shouldn’t be learning) which can lead to disastrous predictive power.

In his podcast, Gigerenzer talks about fast and frugal trees, and says that humans in general don’t use too many data points to make their decisions. Instead, for each decision, they build a quick “fast and frugal tree” and make their decision based on their gut feelings about a small number of data points. What data points to use is determined primarily based on their experience (not cow-like experience), and can vary by person and situation.

The advantage of fast and frugal trees is that the model is simple, and so has little scope for overfitting. Moreover, as the name describes, the decision process is rather “fast”, and you don’t have to collect all possible data points before you make a decision. The problem with productionising the fast and frugal tree, however, is that each user’s decision making process is different, and about how we can learn that decision making process to make the most optimal decisions at a personalised level.

How you can learn someone’s decision-making process (when you’ve assumed it’s a fast and frugal tree) is not trivial, but if you can figure it out, then you can build significantly superior recommender systems.

If you’re Netflix, for example, you might figure that someone makes their movie choices based only on age of movie and its IMDB score. So their screen is customised to show just these two parameters. Someone else might be making their decisions based on who the lead actors are, and they need to be shown that information along with the recommendations.

Another book I read recently was Todd Rose’s The End of Average. The book makes the powerful point that nobody really is average, especially when you’re looking a large number of dimensions, so designing for average means you’re designing for nobody.

I imagine that is one reason why a lot of recommender systems (Netflix or Amazon or Tinder) fail is that they model for the average, building one massive machine learning system, rather than learning each person’s fast and frugal tree.

The latter isn’t easy, but if it can be done, it can result in a significantly superior user experience!

Libertarianism and rejection of authority

Ok so this is yet another of those self-reflective posts, where I try and rationalize why I’m the way I am. And in the process concoct a fancy theory.

I’m part of this secret society most of whose members are libertarian. I must in fact credit this society from changing my ideology from one that was broadly conservative to broadly libertarian (notice that my economic ideology hasn’t changed, only the social bit has). One thing common among most members of this society is that they are the kind of people who don’t bow to authority. They can be described as confrontationalist, or maverick,  or non-conformist. And most of them are libertarian.

I must mention that for purposes of this post, I define libertarianism as a “belief in free markets and free minds”.

In The God Delusion, Richard Dawkins writes that one of the things that makes people religious is the tendency to listen to “superiors”, “elders”, etc. He argues that this is consistent with natural selection – that back in those days where we were a “hunting ape”, if we were the type that didn’t listen to our parents, there was a greater danger that we’d fall off trees or got eaten up by lions. So us human beings are “naturally conditioned” to listen to “elders”, “superiors”, etc. Effectively, we are conditioned to take orders. Dawkins talks about how this makes us religious, but that is not relevant here.

So we grow up having this “elderly authority” at home. The “elderly authority” commands us and guides us and gives instructions, and in return provides us protection from the outside world. Soon we grow up, and don’t need that protection any more, so we don’t need to take instructions any more (if you look at taking instructions from parents as the “cost” of the protection they offer you). But then we are conditioned to taking instructions, and being controlled, and it is tough for most of us to outgrow this conditioning.

And so some people look to “society” to provide the instructions, and control you, and tell you what to do and what not to do. They end up as conservatives. Some other people, look to the government (remember that today’s “government” is a replacement for yesterday’s “king”, who was supposed to be “divine”) for instructions and control. They end up being “liberals” (quotes because traditionally liberals supported free markets; it’s only recently they’ve taken a socialist turn). It is quite interesting that a lot of “liberal” people, who profess their rejection of authority, think it is ok for the government to tell them who to do business with, and at what price.

And then there are these really masochistic people who look to both “society” and “government” to put controls on you. Think Swadeshi Jagran Manch and similar institutions.

And so what about people who actually reject the need to have a “protector” once they grow up? They don’t want to take instructions from anyone, and in return they are willing to forego protection – apart from asking from the government protection in terms of defence, foreign policy and upholding of law. Given that very few people reject authority (Dawkins’ concept), it’s very few people that end up as libertarians.

PS: Is it a coincidence that so many very good libertarian bloggers (Caplan, Tabarrok, Hanson, Cowen) are at the little-known George Mason University, and not at one of the “top-ranked” universities?

PS2: I think large corporations are not free-market in any sense. Leave aside crony capitalism. Corporations, by definition, are internally deeply socialist. I guess I’ll save that for another post.