Comment by YeGoblynQueenne

>> The connectivists left the 'AI' folks and established the ML field in the 90s.

The way I know the story is that modern machine learning started as an effort to overcome the "knowledge acquisition bottleneck" in expert systems, in the '80s. The "knowledge acquisition bottleneck" was simply the fact that it is very difficult to encode the knowledge of experts in a set of production rules for an expert system's knowledge-base.

So people started looking for ways to acquire knowledge automatically. Since the use case was to automatically create a rule-base for an expert system, the models they built were symbolic models, at least at first. For example, if you read the machine learning literature from that era (again, we're at the late '80s and early '90s) you'll find it dominated by the work of Ryszard Michalski [1], which was all entirely symbolic as far as I can tell. Staple representations used in machine learning models of the era included decision lists, and decision trees, and that's where decision tree learners, like ID4, C45, Random Forests, Gradient Boosted Trees, and so on, come; which btw are all symbolic models (they are and-or trees, propositional logic formulae).

A standard textbook from that era of machine learning is Tom Mitchell's "Machine Learning" [2] where you can find entire chapters about rule learning, decision tree learning, and other symbolic machine learning subjects, as well as one on neural network learning.

I don't think connectionists ever left, as you say, the "AI" folks. I don't know the history of connectionism as well as that of symbolic machine learning (which I've studied) but from what I understand, connectionist approaches found early application in the field of Pattern Recognition, where the subject of study was primarily machine vision.

In any case, the idea that the connectionists and the symbolists are diametrically opposed camps within AI reserach is a bit of a myth. Many of the luminaries of AI would have found it odd, for example Claude Shannon [3] invented both logic gates and information theory, whereas the original artificial neuron, the Pitts and McCulloch neuron, was a propositional logic circuit that learned its own boolean function. And you wouldn't believe it but Jurgen Schmidhuber's doctoral thesis was a genetic algorithm implemented in ... Prolog [4].

It seems that in recent years people have found it easier to argue that symbolic and connectionist approaches are antithetical and somehow inimical to each other, but I think that's more of an excuse to not have to learn at least a bit about both; which is hard work, no doubt.

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[1] https://en.wikipedia.org/wiki/Ryszard_S._Michalski

[2] It's available as a free download from Tom Mitchell's wesbite:

http://www.cs.cmu.edu/afs/cs.cmu.edu/user/mitchell/ftp/mlboo...

[3] Shannon was one of the organisers of the Dartmouth Convention where the term "Artificial Intelligence" was coined, alongside John McCarthy and Marvin Minsky.

[4] https://people.idsia.ch/~juergen/genetic-programming-1987.ht...