Research does not say that people produce more when working 40 hours per week
TL;DR: you can get more done if you work 60 hours instead of 40 hours in a week, but the work done in that extra 20 hours might be a small fraction of what gets done in 20 hours during a 40 hour week.This is self-evidently true for many jobs. E.g., if you pick apples for 40 hours, then even if you only pick one apple per hour after that, you will still pick more apples working 50 hours than 40.We software developers, though, have an additional consideration: creating software bugs which can (easily) push the productivity of a given period of time into the negative, sometimes deeply.In my apple-picker example above, this would be like the tired picker driving the loaded apple truck off a cliff, destroying all the apples picked in the first 59 hours of the 60 hour work week (along with the expensive truck).That example is contrived and unconvincing for the apple picker case, though; nobody makes their tired apple pickers drive the apple trucks back via treacherous mountain roads after a hard day of work.That's not the case for software development, however; looking at my own 20+ years of professional software development through the lens of an extremely rigorous scientific n=1 anecdatal analysis (which undoubtedly thrills the OP hehe), in my own career probably 75% of the negative productivity caused by bugs I've created was the direct result of code I wrote while trying to work more hours than I should.I suspect this holds true for other programmers as well.