cognitive psychology. PhD 
As I spend my Saturday night proving properties of the type system for an imperative programming language, my main takeaway is that imperative languages were a terrible mistake and should be banned
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Most people who take OS don't build OSes, but many love the unique challenge of tricky, holistic system design. I see PLT as the same but for thinking mathematically about programming, which is an equally valuable soft skill.
At CMU, companies heavily recruited OS students b/c they were the best engineers. I see a world where PL students are recruited as the best architects, b/c they know how to design modular systems/DSLs, carefully articulate software properties/behavior, etc.
