A lot of the ML techniques we're putting to use today came out of papers from the 80s. These techniques weren't practical to do much beyond toy examples, but they were proven to work. Now, we're able to use those very techniques to teach a machine to identify cat videos with 75% accuracy using unsupervised learning! [0]
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[0]: https://www.wired.com/2012/06/google-x-neural-network/